BMW D7 & D12 MARINE ENGINE

 WEBSITE FOR OWNER'S

Tell me about your problems and successes with your BMW marine diesels. If
you are no longer interested, just tell me and I will remove your name from
my list. If you sell your boat or engine, please send me details of the new
owner. If you know of another owner with one of these engines, please let
me know. There are owners on my list from all around the World, but
presumably numbers of these engines will slowly dwindle as old-age takes
its toll.

George Huxtable

Contact George Huxtable by email at george@huxtable.u-net.com,

by phone at

01865 820222 (from outside UK, +44 1865 820222),

or by mail at

 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
 

"I'm 70 years old, and look exactly like Father Christmas, but without the benevolence."
 

As for our boat, she's an Invicta, one of the early Tupperware designs, by Van de Stadt. Built in 1967, we've owned her since '74, and I fitted the D7 in 1980.

Very like a Folk boat in shape, 26 ft long, narrow-gutted with only 7ft 6 in beam, 4 ft draught. Long keel, ending in a large rudder pivoted at 45 degrees. A fine sea-boat. That's our "Christina".

BMW D7 Engine Manuals

D7 Owner's Manual    These manual's are provided courtesy of Peter Hoare

D7 Workshop Manual    

D7 & D12 Part's Manual

THE D7 AND D12 MARINE DIESEL ENGINES

FROM BMW.
Also some stuff on the similar engines from Renault Marine, the "Couach"
RC8D and RC12D.

A fact sheet for owners, compiled by George Huxtable. <george@huxtable.u-net.com>

This is Issue 4b, which was updated 7 May 2005.


This in being sent out to all owners of D7 and D12 engines on my e-mail
list. If you no longer have this engine, or don't want any further
information, just let me know. I am interested to keep in touch with owners
of these engines, so please let me know how you and your engine are getting
on. If your engine has a new owner, please pass on to me his
name/address/phone number/email. If you know of other owners of these
engines, please pass on their details and I will add them to my list.

                                -----------------------
GENERAL
I fitted one of the first BMW D7s to my Invicta, back in 1980, so it's now
given me 21 years of pretty trouble-free operation. But not without a
problem or two on the way...

The BMW D7 diesel engine is based on a design by the German firm of Hatz,
type HE673, originally intended for use on building sites for cement mixers
and that sort of thing. It was marinised and rebadged by BMW Marine for
powering small craft. Another marine power unit, the Renault-Marine Couach
RC8D , was based on the same Hatz engine, and has a better alternator, but
a worse hand-starter, than the D7 (see below). Both manufacturers provided
larger, 12-horse, marine engines, which seem to have sold in smaller
numbers.

I will concentrate on the D7, which I know well, but many of the comments
that follow apply to its larger brother, the BMW D12, and also to the
Renault RC12D, both based on the Hatz HE780 . BMW's Marine Division had a
short life and no longer exists, and the engines have been unavailable for
many years. I understand that they were fitted for a time to new Sadler
26s, but later dropped, presumably because of the charging problems
referred to below. There's a racing sailboat in the US, the S2 7.9, many of
which have been fitted with a D7 engine.

These are unusual engines in several respects. Normally, when you look at a
single cylinder marine diesel, the first thing you see is a large flywheel
(or its cowl), right at the front, restricting access to the rest of the
engine further aft. In contrast, all these Hatz engines have their flywheel
placed behind the engine, within a bell housing placed between engine and
reduction gearbox. As a result, access to nearly all the engine fittings is
superb; especially so for the BMW versions.  However, the flywheel has a
much smaller diameter, and less inertia, than you would normally expect. As
a result, the engine can never be throttled  back to the placid "chug,
chug" slow tick over that I envy in my friends' craft; or it would be
leaping about on its rubber mounts and threatening to shake the boat to
bits. It's necessary to settle for a rather brisk tick over, and then the
engine remains well-behaved.

The slim profile of the D7 and its easy access from forward were my main
reasons for choosing it to replace my troublesome 2-stroke all those years
ago (a decision I've never regretted). The Invicta is a Van de Stadt
long-keeler, 8m long but less than 2.3m beam, very slim and tapered at both
ends. As a result, there's little width for an engine below the cockpit.
With most small diesels, the engine box would have to intrude into the
cabin, but the D7 just squeezes into the narrow space aft, that the old
2-stroke once occupied.

SOME DESIGN CHANGES.
My D7 was one of the earliest to be produced. Since then, I know of a few
modifications, which were made to later engines.

The cylinder head gasket is a narrow copper ring, 1.5mm thick. There's a
rubber o-ring in a groove around the outer edge of the water jacket to
contain the coolant. On later engines, but not on mine originally, there's
an additional wide copper ring which encircles the head gasket and intrudes
into the coolant space. Because it is only 1.2 mm thick, this extra ring is
not firmly clamped, and doesn't seal to anything. Its purpose, as far as I
can tell, is to divide the coolant space into two parts above and below the
level of the head gasket, while allowing free flow between them. This (I
guess) is to improve the flow pattern of the coolant and the heat transfer
from the head, particularly under conditions where the vessel is heeled. As
I had once heard protests from the engine when I used it to assist when
sailing close-hauled and heeling (not good practice anyway) I have
retro-fitted this copper ring when the cylinder head was off.

In addition, on my early engine there's a very small hole drilled in the
cylinder head casting, to emerge through the face of the exhaust manifold
flange. This matches a hole in the exhaust gasket, and on my original
exhaust elbow there's a matching hole which allows a flow of water through
into the jacket of the elbow, and so out to the exhaust injection. I
guessed that this was intended to allow any air that might get trapped in
the coolant space above the cylinder to be expelled (this seemed a good
idea, to me).

When the first exhaust elbow had to be replaced because it had corroded
away, I found that in the replacement this bleed hole had been omitted.
(The newer design has quite a different shape of casting. In the early
design, as soon as the elbow bends to point aft, it immediately slopes
downwards at 45 degrees. The newer elbow first drops vertically down for a
few inches before turning aft and sloping down). I found that by drilling
through the joint face of the elbow in line with the bleed hole in the head
(using the gasket as a guide) I could reinstate the original air-bleed into
the cooling jacket of the elbow. Whether this has had any benefit, I don't
know, but anyway it seems to have done no harm.

Most of these BMW engines were fitted with the Hurth HBW50 gearbox. See
comments below about the poor choice of gear ratios. Some later engines
were fitted with a different gearbox, badged by the German firm ZF (who now
also own Hurth) but actually made in Spain, type BW3. It uses a triple
chain drive for reverse. This gearbox has a better choice for the reverse
ratio of 2.27, sufficiently close to the forward ratio of 2.75. To
accommodate the different dimensions of the ZF gearbox, the bell housing was
redesigned, and a different torsion coupling was used. The parts list
indicates that changes were made to the flywheel at the same time, perhaps
to accommodate the new torsion coupling.

Later engines than my early D7 were fitted with a fan-ring attached to the
flywheel to help to ventilate the alternator. This was missing on my engine
but after the first failure of the stator windings (see below), I
retrofitted a fan ring. However, it didn't prevent a second failure of the
stator, indicating that heating of the coils was not the problem.

I don't know enough about the D12 to comment on possible design changes to
that engine.

LUBRICATION

Another unusual feature of these engine is their simple splash-lubrication
system. Normally, a marine diesel has an oil-pump, pressure alarm, oil
filter: but not the D7, none of those things. Instead, the con-rod is
extended below the big-end to carry a dipper, a metal scoop which on each
turn of the engine, picks up a spoonful of oil and hurls it around the
inside of the crankcase. This system has given no trouble to me, nor to the
many D7 owners I have been in contact with. Of course, having no
oil-pressure alarm (because no oil-pressure) implies that one gets no
warning if the oil level should run low, which it never has yet.

My owner's Manual recommends that the oil is changed every 50 engine hours
or at least once a year. This may be good advice as there is no filter to
prevent sludge accumulating in the sump, but the oil in my own engine gets
changed rather less frequently. It's an awkward business getting the old
oil out of the sump with a suction pump, and I suspect that quite a lot
remains behind. Has any owner invented a scheme for extracting the last
drops?

A reason for changing the oil before the winter lay-up is to minimize
corrosion caused by the oil's acid content (a product of burning diesel
fuel). Wherever low-sulphur fuel is available, I suggest it would be wise
to use it, and then perhaps the oil could be changed less frequently.


HAND-STARTING

There's a regrettable tendency in modern diesels  to omit any hand-starting
provision. In that case it becomes vital to maintain enough energy in a
separate starting battery, with diode splitters and the rest. In contrast,
the D7 offers easy hand-starting, ingeniously contrived. Because the
flywheel is so small, it needs a good fast spin to acquire enough energy
for reliable starting, so it's geared up to make four revs of the engine
for each turn of the handle, which feels just about right. The handle
itself is a sturdy man-sized job, and there's an automatic decompressor
which can be preset to cut-in the compression, on its own, after a chosen
number of turns. The result is that a skipper can achieve reliable
hand-starting with no requirement to be a Hercules. (The comments above
apply to the BMW version, but not to the Renault 8D, which has
hand-starting provision only by a pull-cord; quite inadequate for a diesel,
in my view.) In addition, the direct injection system, in which fuel is
sprayed into a small well in the piston crown, avoids the need for a
glow-plug, so starting can be done with no need at all for electrical
power. As a result, if my one battery runs flat, I just don't care.

As a final touch, there's an arrangement where, on pressing a plunger, a
small cup of oil runneth over, to be squirted in via the inlet valve and
anoint the cylinder head to assist starting.

If you ever have difficulty in starting, here's a tip, which applies to all
marine diesels. Before you do a lot of turning of the engine, turn off the
cooling water inlet. Otherwise, you could be pumping a lot of water through
the engine into the silencer, which may not be expelled until the engine
gets firing properly. In the worst case, you could flood the exhaust system
and then flood the engine. Cooling isn't needed until the engine fires up.
When it does, don't forget to turn the cooling inlet valve on again.

ELECTRIC STARTING

This is by a Bosch solenoid-starter combination, which I understand is, in
the D7 engines, compatible with the starter that was fitted to older VW
Beetles (not the very oldest ones, though, which had 6 volt electrics!).
The only problem I have found is that after a few years in a marine
environment, the high-current copper contacts within the solenoid start to
corrode, and fail to close properly. The solenoid can be heard to pull in,
but the starter doesn't turn. This can be very damaging in causing
inductive sparking and high back-voltages elsewhere. The contacts are
easily cleaned up after dismantling the solenoid (this needs a fattish
soldering iron), and then they are good for several more years. Until it
happens again.

One problem that was reported to me is of a starter on a D7 which wouldn't
release when the start button was let go, and kept turning the engine. As
there was no battery master switch in the installation, this caused serious
damage by the time the circuit was broken. There's a lesson here...

THE ELECTRICAL GENERATOR AND ITS PROBLEMS

This section refers to BMW engines only; the Renault versions use a
conventional external alternator, belt-driven.

It's time now to turn with regret to the "Achilles heel" of the BMW
engines, their electrical charging system. Instead of using a standard
alternator, as do most car and boat engines, the D7 hides its electrical
generation within the flywheel, as a stator carrying coils which are
energized by permanent magnets rotating with the flywheel. Neat and
compact, but that's all there is to be said in favor of this flawed
system.

It's highly inaccessible, for one thing, in that the gearbox and then the
flywheel have to be parted from the engine to get to the generator.  Being
single-phase only, current flows to the battery as a succession of separate
pulses rather than the nearly-steady output of a normal 3-phase system, so
more ripple can be seen on the battery voltage. There's a separate
"control" winding which can develop 220 volts AC, and could be lethal to
anyone who happened to span the control terminals.

To limit output when the engine speeds up or the battery nears full charge,
on each cycle a short-circuit is suddenly applied across this control
winding for a short time by means of an electronic switch (triac). This
causes a dc bias current to build up in the control winding, which results
in a magnetic bias which saturates the iron stator on alternate
half-cycles, and reduces the output. The spikes that this brutal action
creates appear across the battery and cause interference that ruins
reception of radio, and probably Loran and used to affect Decca (but not
GPS). The output of the charging system is rather puny; with my nav lights
on, there was little extra left for the battery. And it's unreliable, as I
will explain.

After using my D7 for a few years, one day the charging output suddenly
fell to zero, which was traced to shorted turns on the control winding,
caused by insulation breakdown of the high-voltage turns. The stator was
replaced, at considerable expense, by a new one with redesigned coils,
neatly encapsulated. These were supposed to cure that problem, but failed
again, in the same way after a couple more years. Since those days I have
been in touch with many other D7 owners who tell the same tale. Sometimes
the cause has been ascribed to implausible events such as "the flywheel
magnets becoming demagnetized" but my bet is that each time the culprit has
been the same; insulation breakdown in the control winding. After talking
to many D7 owners, my own guess is that more have suffered this problem
than have escaped it.

DRIVING AN EXTERNAL ALTERNATOR

After the second such failure, I refused to throw more good money after
bad, and remembered a cutting I had filed away back in 1990, a letter to
Practical Boat Owner from Mr D J Unsworth, of Bridport. He described how he
had chucked out the stator, magnet ring, and fan ring from the flywheel of
his D7, and instead fixed a v-belt pulley wheel to the inside of the
flywheel. A V-belt, driven by this pulley, emerged through the vent slot
above it, and turned the pulley-wheel of a car alternator, placed behind
the cylinder and above the flywheel. The vent slot becomes visible when you
remove the cover-plate carrying the regulator, etc, just behind the
cylinder.

About five years ago, I followed Mr Unsworth's scheme, with complete success.

To do the same, you would need to be (or, as in my case, have a friend who
is) a good machinist. If any reader is interested in hints and sketches
about doing the job, I am happy to cooperate, but there aren't precise
drawings as it was all made rather ad hoc. There remains a snag, in that
the drive belt is trapped in place, and gearbox and flywheel need removing
to replace it when it has stretched too far. However, I have since invested
in a detachable link-belt, and hope that this can be fitted instead,
without dismantling, when the time comes. We shall see.

For my own version, I had available a piece of very thick-wall steel
tubing, which could be turned down to 100 mm inner diameter, 126 mm outer,
and about 60 mm long. One end of this tube was butted up against the inner
radial face of the flywheel. A shallow circular groove was carefully
machined in the cast surface of this face to receive the end of the tube
(it's important that this groove is exactly perpendicular to the flywheel's
axis). Threads (6mm) were tapped into holes in the end of the tube.
Corresponding holes were drilled through the flywheel, on the same pitch
circle, and interleaved between, the bolts that hold the drive plate to the
opposite face of the flywheel. To accommodate the heads of the high-tensile
bolts used to fix the new tube, it is necessary to grind away some notches
from the outer edge of the drive plate (its material is too hard and
intractable to allow anything else). A vee groove, depth 8mm, to
accommodate the v-belt, is machined in this tube, centered about 48mm from
the inner face of the flywheel,  so that the belt can clear the edge of the
flywheel. The end of the tube requires beveling off on its inner edge, to
avoid contact with a conical bearing housing. Dimensions given are
as-drawn, but perhaps not exactly as-made, so care should be taken to
ensure everything will fit.

The new flywheel-pulley is meant to align with the ventilation slot in the
casting, behind the cylinder, but this slot isn't quite wide enough to
allow enough clearance for a standard v-belt and needs some enlarging with
a file in the appropriate places (not a major job, I found).

I chose to use the alternator from an old car (Vauxhall Astra, = Opel),
with its mounting pivots and slotted adjustment. A suitable bracket will
need making to mount these to the engine, and care is required here.
Because a single-cylinder diesel shakes about so much more than a
four-cylinder car engine, the mounting points on the engine need to be
strong and well-spaced to resist the vibration forces.

A v-pulley of about 76mm outer diameter was fitted to the alternator,
because that was the size I had. With hindsight, I would now choose a
somewhat larger pulley, to reduce the step-up in speed.

I could, if asked, suggest other ways of fabricating a pulley attachment to
the flywheel to avoid some of the machining that was called for in this
design.

D7 engine: Instructions for making a vee-belt drive to an external (car) alternator.

Click on drawing to view full size
I sent this note, since slightly amended, a few years ago, to a D7 owner in
the UK who ran a garage, so had skills and tools for some machining.

Here's the story, as well as I can recall, about the fitting of belt drive
to an external alternator on the D7.

The BMW D7/D12 parts manual, available via this website, gives useful
exploded drawings.  I will refer to parts by their drawing no / part no,
such as 11/1/1 for the crankcase casting.

In theory, one can leave the gearbox and bell housing and engine mountings
all in place, and simply unbolt and remove the engine from the bell housing.
Reassembly, after the job is done, is somewhat more tricky, as there is no
beveling on the splines to give an easy re-entry. What makes the
reassembly particularly awkward is that the 4 mounting bolts between engine
and gearbox have to be aligned to enter at the same moment as the splines
engage. So everything has to be aligned exactly; not that easy when you are
taking the weight of the engine! So, on balance, I have found it easier to
remove the whole assembly, engine and gearbox together. Then, afterwards,
it's much easier to offer up the gearbox to the engine rather than vice
versa. That's what I've found, anyway.

>From the parts lists and their exploded diagrams, it appears that on later
engines the two upper mounting studs between engine and gearbox have been
increased in length. This would be most helpful when reassembling, as the
engine could be easily maneuvered over these two long studs first, and could
then hang from them while the other studs and the splines are brought into
engagement.

Once you've got the engine out, getting the thing apart is very
straightforward.  Unbolt the bell housing from the engine (4 bolts) and pull
the gearbox off the splines.

There are 4 long bolts through the flywheel hub, 11/9/14.  These are rather
tight, and the hex heads are shallow. Because a standard hex socket is
beveled internally at its end, it doesn't get a good purchase on the
shallow hex head and tends to jump off it when you clout the wrench handle.
It helps to grind 2 or 3 mm off the end of the socket to remove this
beveling, so that it's a close fit along its whole length. Take the
flywheel off.

Remove the six socket screws and discard the fan ring. (This fan ring
wasn't fitted to early engines such as mine, though the threaded holes
existed in the flywheel. At one stage, I retro-fitted a fan ring in a vain
attempt to improve alternator life by getting better cooling.)

Pull out the hairpin clip with pliers and discard the magnet ring.

Undo  any clamps 12/1/5 for the stator cable and the four hex screws 12/1/3
and discard the stator. Remove hex screws 12/1/6 and discard the mounting
plate for the electrics with all its components (12/1/8 or in its latest
version 12/3/1). There's an intermediate version, drawing 12/2, which I
haven't copied.

>From the flywheel, remove (but keep) the 4 socket screws that retain the
drive plate.

Having done all this, the slot in the casting, through which the stator
cable passes, is clear to see and to get at. It's not shown on any
diagrams, but on drawing 11/1 it lies just below where the figure 1 points
to on the crankcase. It's through this slot that the vee-belt has to pass.
As I remember, it's only about 10 mm wide, not enough for a vee-belt to
pass without binding, so it's necessary to open it up a bit with a coarse
file, by 2 mm or so (I'm guessing here) on either side. In my judgment,
doing this didn't compromise (much) the strength of the casting. It doesn't
need to be widened over the complete length of the slot, just the central
part where the vee-belt will pass. You will need to prevent the filings
from getting where they shouldn't.

According to my notes, the centre line of a vee-belt which passed through
this slot  would be 9mm forward of the forward face of the flywheel,
allowing about 4mm clearance between the aft edge of the belt and the
flywheel - just nicely clear, in fact. This would put the mid-plane of the
belt some 48mm forward of the interior surface of the web of the flywheel.
My sketch should make this clear.

Now we get to the more tricky part, the mounting of a pulley to the
flywheel. I have a friend, Tony,  who is a skilful machinist with some good
machine tools. The sketch, "flywheel.jpg" shows how it goes together, but
is not intended to be a precise drawing for machining or assembly. Please
don't take any dimensions in this note as "gospel" without checking
clearances for yourself on your own engine.

I happened to obtain a piece of heavy-wall steel tube, 100mm ID, which we
trimmed down to 127mm OD, and 60 mm long. We decided to fit this tube by
butting it to the inner radial face of the web of flywheel, and drilling  4
fixing holes through the  flywheel, on the same pitch circle as the fixings
for the drive plate but interspaced between them around the circle, through
which 4 6mm bolts would go into corresponding holes tapped into the ends of
the new tube.

The interior radial face of the flywheel appears to be just as-cast, so we
decided to true it up by machining a shallow recess in it to take the new
tube, as it's rather important that the tube, which will become the drive
pulley, is really coaxial with the flywheel centre-line, or the pulley will
wobble. This groove was made 2.3 mm deep, with ID and OD to just fit the
end of the tube, so that it was well located. I understand that Tony made a
special jig to go into his chuck, with a plate to accurately pick up on the
4 holes (for the drive plate which couples to the gearbox input), which are
presumably well centered. He then checked that the forward end of the
flywheel's spindle ran exactly true before machining the shallow groove.
He's a very careful fellow!

Now a standard vee-belt groove has to be made in the tube, with its centre
line 50.3 mm from the end where the tube butts to the flywheel (48 mm as
before, and 2.3 mm extra because of the depth of recess).

I had intended to drill 4 additional holes through the drive plate
(coupling to the gearbox) so that the 6mm socket screws which fix the new
tube would pass through both the drive plate and the web of the flywheel.
However, the material of the drive plate is so hard that none of my drills
could even mark it!. So instead, I just ground away some triangular notches
in the outer rim of the drive plate to allow room for the heads of the
high-tensile socket screws, so they no longer pass through the drive plate.
You would make a better job of it by milling out recesses in the flywheel
so that the caps of the four new socket-screws can be fully recessed, and
then the drive plate can go back flush over them.

You will note that the forward end of the new pulley tube has been beveled
away at 45 degrees or thereabouts. There's a reason for this. If you look
at part 11/9/17, you will see that this flange protrudes aft somewhat,
toward the interior space occupied by the pulley. There are some
strengthening webs cast into it, which give it a tapered profile. It served
two purposes, to retain and seal the crankshaft bearing and to providing a
seating for the stator of the generator to bolt to. I don't know exactly
how its dimensions fit to my drawing, but the bevelling was to avoid any
contact with this flange. And missing this flange was also a reason for
choosing the shape and size of pulley as we did.

Of course, now there's no stator any more, the aft part of this flange is
no longer needed, and the flange could be removed and its after part could
be machined (or even hack sawed) away to avoid any conflict. This becomes
more relevant if you consider mounting the pulley in a different way to
mine: see below. Note that the flange referred to above is shown also on
another drawing (12/1/25), in which it has a different part number. I
suspect that drawing 12/1 might have originally been made to show mounting
to a different engine, and 11/19/7 is correct. You can see the flange, with
its tapered webs, on drawings 20 and 21, page 14, in the workshop manual
for the D7. If you don't have that manual, don't worry; it will become
clear as you dismantle.

I presume that you can decide best how your chosen external alternator can
be fixed and adjusted, and how the electrics should connect. This is all
standard practice. You don't need advice from me. But I would select the
lowest-powered alternator I could find.  I happened to have an old Vauxhall
(same as Opel) that had reached end-of-life, so I removed the alternator,
with all its mounting hardware. This was rated at 45 Amps output, which is
more than adequate, unless you have an immense battery-bank to charge. The
smaller and lighter the alternator, the better.

 There's a tendency in modern vehicles for the alternator to be driven by a
flat multigroove belt rather than a vee-belt, but there's certainly no room
for such a flat belt to emerge through the slot behind the cylinder. If you
have such an alternator, you will need to find a vee-belt pulley instead.

My first vee drive belt lasted a few years, but then I replaced it with a
vee-belt made of segmented links, which can be detached. This allows the
belt to be removed and replaced by wheedling it out, still leaving engine
and gearbox in place, which is a great advantage. To start with, I was
worried about how long such a segmented belt would last, but it seems to be
holding up well.

One thing I would change. I would alter the pulley sizes to reduce the
speed step-up. Why? Well, the D7 labours in reverse because of its strange
gearbox ratios and is often on the verge of a stall. With a low battery, or
a lot of electrics switched on, the alternator needs a lot of torque to
drive it when the engine speed is low. This can be enough to tip the engine
into a stall. I have arranged a switch coupled to the reverse lever that
cuts out the alternator field current (and hence the torque) to avoid this
problem. Reducing the drive speed of the alternator shouldn't cause
problems. Tick over speed of the D7 has to be quite high anyway (because
otherwise it shakes about so much) so there should still be reasonable
charging at tick over speed.

In my installation the driving pulley has a radius of about 56mm. (that's
the mean radius at halfway down the vee groove) and the driven pulley about
34mm., so giving a speed step-up of 1.65 or so. At the lowest tick over
speed the D7 will run at without shaking the boat to bits, the alternator
is then quite capable of stuffing 25 Amps into a low battery or a load. If
I were doing the job again, I would choose more equal pulley sizes, perhaps
a step-up of 1.2, maybe even less. This might then require a rather higher
engine speed when charging the battery. The advantage would be less torque
loading on the engine from the alternator.

Instead of the heavy steel tube that I adapted, which called for quite a
but of machining, you could get a similar result in different ways. You
could fabricate the thing by welding a thinner tube to a pulley at one end
and a flange at the other, but they would need to be carefully machined
true afterwards. Or you could arrange to firmly clamp a pulley to the
cylindrical surface of the spindle of the flywheel , as described below
(easiest to visualize when you have it all apart).

As I remember it, the spindle of the flywheel has a nice smooth outer
surface 65mm dia. or thereabouts, and is probably machined to be coaxial
with the axis (but this needs confirming: if it isn't, it might call for a
skim to true it up). A pulley with an accurate bore to this shaft could be
slid on, and clamped in place at the appropriate position. How would you
design the clamping? Well, the pulley might perhaps be sawn in half, and
clamp bolts to compress the halves together, rather on the lines of the
clamp between a drive flange and a prop shaft, (but with much less arduous
loadings). This would leave some small gaps in the pulley surface which
might affect belt life (but I doubt it). Alternatively, one could design a
pulley with a well-fitting hub that slides over the spindle, but with an
extension to one side of the hub which is cut to make it springy and
clampable to the shaft. Perhaps a stainless hose-clip could be used around
this split hub to clamp it tight.

Or perhaps you could clamp the pulley hub to the shaft with a wedging
cotter-pin like you have on the pedal cranks of a bicycle. Or perhaps more
simply you might just have a radial clamp bolt (or two) that's tapped
through the hub of the pulley and engages into a dimple or two in the outer
surface of the shaft, that you would have to drill. Not too demanding.
However, you would need to keep in mind the protruding part of 11/9/17 to
avoid any clash. Part of this could perhaps be sawn off or turned off if
necessary.

However you decide to make and fix the pulley to the flywheel, you should
measure carefully first to ensure that the belt will emerge centrally
through the (enlarged) slot behind the engine. Don't just blindly copy the
dimensions shown on my sketch. These show the pulley arrangement as
designed, but not necessarily exactly as-made. Some of the dimensions may
have been adjusted slightly, by a mm or so perhaps, to put the belt in
exactly the right place. You should do the same

I don't think you need to be very careful about preserving precise balance
of the whole assembly, however the job's done. After all, a single-cylinder
engine is, by its nature, fundamentally unbalanced anyway, and there's
nothing can be done about that! But don't add any gross imbalance.

I wanted to avoid any possibility of oil accumulating in the bell housing
and perhaps contaminating the belt, in case of leakage through the seals on
the crankshaft or the gearbox input shaft , so while it was apart I drilled
a drain hole at the lowest point.

The details of fitting the alternator will vary depending on the dimensions
of the alternator and the mounting hardware that comes with it, so that's
left up to you. Do provide a firm mounting base, because a single-cylinder
diesel shakes about so much it could easily break any flimsy fittings, due
to fatigue. Triangulation is the answer! There are many bolts and holes you
can pick up on to fit a mounting frame. Because it's such a business
replacing the drive belt, allow for plenty of adjustment in the slotted
strut as the belt stretches.

 I hope you can cope with the electrics involved, which are similar to the
arrangements for a car alternator.  The alternator's initial excitation
current (which flows through the warning light) has an important function
in triggering the alternator into action on startup, that is seldom
appreciated or understood. On a car this is controlled by the key switch,
which also controls the solenoid allowing fuel to flow. On a boat, the
engine is normally stopped by other means, so the warning-light current may
accidentally be allowed to continue to flow after the engine is stopped,
slowly draining the battery. On my installation there's no key switch, only
a starter button (and the battery isolator, of course). The warning-light
only comes on when a mercury vibration-switch attached to the engine senses
that it's running. It turns off this current through the lamp as soon as
the engine stops.

When running the starter motor to get the engine started, if the alternator
is trying to generate current at that time, it acts somewhat as a drag on
the engine, making the starting process that much harder. I have linked the
starter button in with the warning-light current so that the
field-excitation of the alternator is delayed until the starter button is
no longer being pressed. So only when the engine is fully running does the
alternator drag commence.

The alternator field current is broken by a switch which senses that
reverse gear is selected, so removing the drag of the alternator at the
time when the engine would otherwise be on the verge of a stall.

As you can tell by now, I'm a fellow who likes to tinker!

George.

SOME OTHER ALTERNATOR OPTIONS

There are other, more radical, redesigns which allow a drive to be brought
out to an external alternator. The Renault 8D drives a pulley-wheel from
the forward end of the camshaft, at half engine speed, and the v-belt then
goes in a delta shape, embracing the alternator and a (displaced) water
pump, at the forward end of the engine. This would foul a starting handle,
and the 8D has to make do with a pull-rope for hand-starting: inadequate
for a diesel, I would say.

Another alternative is to use the dog, intended for hand-starting, to drive
a v-pulley, though this also loses the hand-start provision. Unfortunately,
this shaft runs at only one-quarter engine speed, so the pulley sizes have
to be chosen to speed the alternator up. Ian Hopley (ian@ihopley.freeserve.co.uk)
has made this modification to a  BMW D12, using pulleys of 6-inches and
one-inch diameter, which, remarkably, give satisfactory operation. Ian used
a flat grooved belt for this job, not a vee-belt, and this shows what such
a belt is capable of.

 Another mod., on similar lines, has been made on a D12 by Stan Duggan in
Nova Scotia (sunebank@supercity.ns.ca). He has taken a drive from the
starter dog, using standard Volkswagen golf components with a vee-belt and
a 2 to 1 step up, to drive an alternator. This has allowed him to retain a
usable starting handle. He says that he needs a lot of engine revs to
achieve good charging. He has plans to change this arrangement in favor of
a belt-drive from the camshaft.

There are significant differences in the geometry of the D7 and the D12,
around the starting handle region, which can make a solution for one
inappropriate for the other.

Another proposal has been made for the D7, which I think would work, as
follows- remove the water pump from its normal (BMW) position driven from a
dog at the forward end of the crankshaft, and replace it by a vee pulley
driven from that same dog, at engine speed, which drives the alternator
with a belt. The pulley would require to be mounted on bearings and with an
oil-seal on its drive shaft. Perhaps the water pump could then be mounted
on an outrigger bracket just outboard of its previous position, and driven
via the axis of that new pulley, or else it could be driven by the vee-belt
in a triangular run. It might even be possible to make this arrangement
compatible with the starting handle. I have been in touch with the owner of
a cat in Tasmania with two D7's fitted, both having succumbed to alternator
disease. He is modifying these according to the above scheme, with a
vee-belt in delta layout, hoping to retain hand-starting, and has promised
to inform me about his progress. No results are available so far.

CORROSION

These engines are arranged for raw-water cooling, with two zinc anodes
placed inside the water-jacket. They do a perfect job in keeping the iron
castings free of corrosion, leaving a zinc coating everywhere. I've found a
few replacement anodes, intended for a different engine, going cheap, which
only needed a new thread cutting on them. On my BMW D7, the jacketed
exhaust elbow, which is not protected by zincs, corroded away in 14 years.
This corrosion was eating the elbow away from inside the water passages, so
by the time that discoloration appeared on the surface, there was hardly
any good metal left within. So beware, corrosion of this elbow can come
upon you suddenly! A redesigned elbow casting was expensively obtained,
and is holding up so far. On the Renault engines, the exhaust elbow is
quite a different design. I doubt whether any of the water-injection
cooling elbows, for these engines, is a Hatz product;  more likely, they
were developed in marinisation.

There seems to be a special problem with the cylinder heads on the D12
engine. After some years of use, tiny cracks have developed on several of
these engines between the injector and the exhaust port, due to corrosion
in the water passages. I do not know of any owner who has managed to make a
repair, and I presume that a replacement head is very expensive. If any D12
owner has resolved this problem, it would be interesting to hear about it.

One of my correspondents with a D7 has found cooling water getting into the
sump. This was discovered to be due to corrosion in the exhaust elbow,
allowing water to enter the cylinder via the exhaust valve.

For protection against corrosion and frost over Winter, a common practice
is for an antifreeze mixture to be sucked via the water pump through the
engine with the idea of displacing the existing coolant. To me, this seems
bad practice. Unless the engine coolant is very hot, the thermostat will
always be closed, and so the antifreeze will tend to bypass the engine
jacket and go straight out into the exhaust. For this reason, it seems to
me better to drain the jacket by removing both the lower zinc anode and the
blanking plug above the cylinder head, then after replacing the anode,
refill with antifreeze from the top.

In most installations, the exhaust manifold is connected to a water lock
silencer by a short length of flexible hose. This silencer will inevitably
retain some water. While the engine is idle for long periods, it's quite
possible for some of this water to evaporate and to condense within the
cylinder. So it's wise to arrange that when the engine is laid up, the
shaft is in a position where both inlet and exhaust valves are closed. In
my own engine, this happens to be when the cross-bar on the hand start gear
(that the starting handle dog engages) is horizontal. Yours may be
different.

GEARBOX

The comments below refer to BMW engines; not Renault, which have a 3.07
reduction in both directions.

The reduction gear is the familiar Hurth box, HBW50. Hurth make this in two
versions, offering a choice of forward reduction ratio; either 2.05 or
2.72, and BMW happened to choose the 2.72 version. At first sight, this
seems sensible, as the D7 runs at rather a high maximum speed, 3600rpm, and
the bigger reduction allows a larger, slower-turning, propeller to be used,
giving more static thrust. However, there's a serious problem, in that both
versions of the gearbox offer the same reduction in reverse, of 1.86. And
that makes for a big discrepancy between forward and reverse ratios, 2.72
and 1.86. As a result, it's difficult (perhaps impossible) to select a
propeller that allows the engine to put out anything like its full power in
both forward and reverse.

In my own installation, the prop was chosen to load the engine correctly in
forward gear. As a result, in reverse, the engine tries to spin the prop
much faster, and fails to provide enough torque to do so. So in reverse the
engine labors at about half-speed or less, seemingly on the verge of a
stall. Other D7 owners have told me that their engine commonly does stall
when they select reverse, so that arriving at a berth is a hit-or-miss
affair!

The BMW parts catalogue for the D7 and D12 shows the Hurth HBW50, which is
commonly fitted. It also shows a ZF gearbox (type BW3) as an alternative
fitting, which has a gear drive in one direction and a chain drive in the
other. For the ZF, the forward ratio is the same at 2.75, and reverse has
the sensible ratio of 2.27. I think that the ZF was fitted to some of the
later D7s. Because some dimensions differ from the Hurth box, the
bell housing was redesigned, to put the output coupling and the engine
mountings in the same place for the two gearboxes. The torsion coupling
between flywheel and gearbox also differs. Some changes were also made to
the flywheel, perhaps to accommodate the different torsion coupling. If
anyone on this mailing list has a D7 fitted with the ZF gearbox, I would be
very keen to get a report on its behavior. It will become clear why.

To overcome the problems inherent in the poor gear ratios of the Hurth
gearbox, I have been looking out for a ZF box to try instead. Recently I
discovered Graeme Williams, of Performance Imports Ltd, PO Box 4,Cambridge,
New Zealand. Phone  64 7 8274019, Fax 64 7 8278840, Mobile 64 21 923854.
Email address  graeme.performance@thenet.net.nz. He has acquired a
collection of parts for D7 and D12 engines, and happened to have two such
ZF gearboxes salvaged from defunct D7s. His price, including the necessary
bell housing and coupling disc, was NZ$600, airfreight NZ$255, which seemed
fair enough to me (the NZ dollar is at a low ebb), . The package was
shipped in a few days, so now I am the proud owner of a ZF gearbox. But now
is the start of the sailing season, so fitting it will be a job for next
winter. I've even acquired a photocopy of the ZF manual from the UK agents,
TWMarine, in Derbyshire, UK, phone +44 163 745757, email TWMarine@cwcom.net

I'm taking a gamble that the modifications to the flywheel involve nothing more than
drilling new fixing holes for the torsion coupling. I will report how I get
on in due course.

ENGINE MOUNTINGS

The engines are supported on flexible rubber mountings, but in different
ways. In the Renault version, the forward pads are right at the front end
of the engine. The BMW design for the D7 puts the supports much further
back, so the forward mountings carry nearly all the weight, and they
attach only to the bell housing/gearbox assembly, so the engine itself can
(in theory) be unbolted and removed without disturbing the mountings at
all. I should add that refitting the engine is not nearly so easy;
see" Parting and refitting engine and gearbox", below. Reassembly is much
easier if the complete unit has been removed, as it's far easier to offer
the gearbox up to the engine than the other way round.

I know of one D7 engine in which the rear mounting rubbers were parting
from their metal fixings, with some rust showing. Not a bad record after
about 20 years, and the big front mountings appeared to be holding up well.
But it does suggest that the rear mountings may be nearing their
end-of-life on many engines now, and as this could have dire consequences
for the stern gear, a close look at these mountings might be prudent.
Replacements can be got from P H Marine.

The layout of the rear engine mountings on the D7 is rather odd and to my
mind not entirely logical. There's a horizontal rubber "bobbin" on each
side of the gearbox. As a result, the back end of the engine is very firmly
located in a left-right direction, but very free in the up-down direction,
in which the mountings move readily under shear. It could make more sense
to alter the direction of these rear mounting rubbers so that they were at
right angles to each other, perhaps by putting them into an inverted-vee
configuration. Has anyone tried modifying these mountings?

PARTING AND REFITTING ENGINE AND GEARBOX.

As stated above, it's easy to remove the D7 engine by undoing four bolts,
leaving the gearbox, bell housing, and all engine mountings in place. This
would be very convenient, except that it's so tricky to replace the engine.
When offering the engine to the gearbox, and bearing the weight of the
engine, the four studs come into engagement at almost the same moment as
the gearbox splines are engaged. Getting everything aligned (including
turning the output shaft to align the splines), so that it all engages, is
almost (but not quite) impossible, I have found.

On later engines, BMW appear to have done something to improve this
situation. The upper pair of gearbox-to-engine mounting studs (10 mm dia.)
has been greatly lengthened, to 65mm, so that these can be engaged first,
and take the weight of the engine while the lower mounting studs and the
splined shaft are maneuvered into engagement. Next time I have my engine
apart, I will make the same change. All it takes is a length of 10mm
threaded rod (studding) which can be cut to a suitable length. At the same
time, I plan to lengthen the lower fixing studs, but by less, so that all
the studs are engaged before the splines have to be aligned.

Unfortunately, no easy lead-in has been provided for the engagement of
these splines, and there's a good argument for beveling (with a small
grindstone) the teeth of the splines just as they start to enter.

SELF-BLEEDING?

The fuel injection system has given me little trouble, and other owners
report the same. However, when my engine arrived new from the showroom 21
years ago, I was unable to start it until I had slacked off the pipe to the
injector, in the time-honored way, and bled the air out. This in spite of
the BMW claim that the engine is "self-bleeding". The BMW manual associates
this claim with the presence of a non-return ball valve at the output of
the injection pump. However, I'm aware of three D7 injector pumps, in none
of which does this valve appear to have been fitted, so perhaps the
self-bleeding claim should be taken with a pinch of salt.

STARTING DIFFICULTIES.

Few owners have reported problems in starting these engines, but I have
just heard from an owner in the US who has recently bought a boat fitted
with a D7 and has, as yet, been unable to start it. I have sent some
suggestions for checks of what might be wrong, and in case this might be of
use to others in the same position, it's copied here.

============

Before you indulge in any prolonged cranking, do turn off the cooling-water
intake valve, to avoid flooding the exhaust system and then the engine. And
don't forget to open it again, in the excitement if and when the engine
fires.

Don't believe the claim made by BMW when they say that the engine is
"self-bleeding", and therefore no bleeding of the fuel system is ever
required.

I presume the electric starter is turning the thing over briskly. If not,
you can always help it a bit with the starting handle. Also, I presume you
have proper compression. If so, it should be difficult or impossible to
commence turning with the handle, without using the compression release
knob to allow it to get under way. Presumably, the compression-release knob
itself is working, clicking round as the engine turns.

If the compression is poor it could be because there's some air leakage
past the piston or the valves, and you may be able to help by filling the
oil-thimble above the air intake with lubricating oil (ordinary engine
oil). When the engine is spinning, trying to start, press down the plastic
button to squirt this oil into the cylinder. If this isn't enough to
improve compression, you could remove the injector (see below) and put a
few drops of oil in from the top, but do be careful not to add too much.
The capacity of the cylinder is about 350cc (milliliters) and the
compression is about 20:1 so the volume above the piston under compression
is only 17cc or so. If you were to put in enough oil to fill up most of
that space, you could get hydraulic lockup which may damage the engine. On
the other hand, a few cc of oil will increase the compression by occupying
some of that space above the piston.

Presumably, you are aware of the little round knob to help cold starting,
just forward of the dipstick, which you pull out until it clicks before
trying to start. I think that what this does is in effect to hold the
"throttle" open, whatever the position of the normal speed-control lever.
When the engine eventually fires and gets up to its governed speed, this
knob then releases. When starting, I usually pull out this knob and if I'm
having trouble, also set the speed control to maximum, just to make sure.

However, it's most probable that the problem lies in failure to inject
fuel. Here's what to do.

First, slack off the nut where the injector pipe couples to the injector
(you may have to remove the rocker-cover to get a spanner to bear on that
nut). Now turn the engine, and fuel oil, not air bubbles, should ooze out
from the joint, in spurts. If bubbles appear, keep turning until
(hopefully) they stop and nothing but liquid fuel issues forth. Quickly
tighten the nut again. This bleeding process is essential if any air has
become trapped in the fuel system; don't believe it when BMW state
otherwise..

If you can't get the bubbles to stop, or if no fuel oil appears, then
probably something is wrong with the feed of fuel to the injector pump.
Disconnect the feed pipe to that pump, waggle the lift-pump lever up and
down and you should see nothing but fuel, no air, coming from that pipe. If
not, you have to trace back to discover whether there's a fuel blockage or
an air leak in. A likely possibility for a blockage is the filter under the
cap of the lift-pump. If all's well, reconnect the feed pipe, ensuring that
any hose clip is properly tightened.

If all's well there, you need to check on the injector. Undo the injector
pipe, take off the two nuts, free any stickiness by turning the injector a
bit with a spanner, and it should come free. It's not threaded into the
head, it should twist freely either way when any rusting has been broken.
(On reassembly, slather it all with grease to stop water getting trapped in
the recess around it). Be careful to catch any washers that emerge with the
injector and replace them the same way up in the same order. If they remain
in the head recess, that's fine. Try to minimize the amount of grot that
will fall back in.

If you slack off the injector pipe at the bottom end, you should now be
able to twist that pipe around until you can refit the injector to the top
of the pipe, now not in the cylinder but pointing out into the world. Put a
piece of cardboard or something in the way to catch what squirts out. Keep
your hand out of the way, the pressure in the jet can be so high as to
inject oil through your skin! Do the nuts up tight at both ends of the
injector pipe.

Now when turning the engine you should clearly see a series of squirts of
oil-spray emerge. If that happens, it's not a fuel fault that's preventing
you from starting. You have to look for something else, almost certainly
lack of compression.

It can happen that when an engine is laid up the piston rings get a bit
rusty in the grooves and can't flex to follow the surface of the cylinder.
Or a bit of rust may spoil the fit of the valve seating. If you can get
the engine started at all, that condition may clear as hot oil blows around
as the engine runs. But how do you get that initial start?

I've never tried this, but aerosol cans of an ether mix used to be
available to aid starting of diesels. I haven't seen them in the shops in
the UK for years, but my friends swear that a whiff of ether makes all the
difference to getting a start. If you have a friend who might have an old
can of engine-start in the back of his shed, you could give it a try. At
your own risk, it's VERY flammable stuff. Presumably you fill the
air-filter housing with it beforehand.

However, regarding the suggestion above about using ether,
Graeme Williams, of Performance Imports, New Zealand
<graeme.performance@thenet.net.nz> has responded as follows-

"George, a word of advise, DO NOT use starting fluids ( such as ether ) on engines
with compression ratios like D7/D12 engines have, you can get away with this
practice on early "non pre combustion chamber" or lower compression engines,
but the resulting detonation will do some serious damage to the later models."
Regards Graeme Williams

I'm grateful to Graeme for sharing this knowledge with us, and it seems
good advice to share around.

I haven't tried this one either, but a friend of mine with a big 4-cylinder
job (not BMW) tried as a last resort connecting two 12 volt batteries IN
SERIES (!) to give him 24 volts for starting a 12 volt system, and it
worked. The extra speed of the starter did the trick. After that first
start, it was never needed again. It seems a dodgy thing to do, to my
cautious mind, but if an extra 6-volt accumulator was available, to boost
the supply to 18 volts, I would be less hesitant. It would probably be wise
to disconnect the alternator and everything except the starter for this
trick.

If the fuel is spraying in, and if the compression is intact, it's hard to
see how a diesel can fail to start. But that pious statement might not be a
consolation to you.

I don't know of any BMW owners who have reported a real fault with the
injection system itself. But if you need to contact a Bosch agent, the
following information from the repair manual may be useful-

"Injection pump: Bosch type code PFE 1Q 55/19, Bosch No 0 414 050 996, BMW
part No 1351 1329 656. There is the added statement (which I question
somewhat) "with second hole in the housing (for automatic venting)".
Injector assy: Bosch No 0432 297 022, BMW part no 1353 1329 667.
Nozzle: Bosch type code DNO SD 21, Bosch No 0434 250 001, BMW part no 1353
1329 669.
Injection pressure 135 (+8) bar."

It also adds that you can adjust the injection pressure by adding shims at
the spring, and that a shim thickness of 0.1mm changes the pressure by
approx 15 bar. However, I know of no owners who have had to make such
adjustments, and somehow I think that there would have to be a major fault
to prevent you from starting at all. And I doubt of any pleasure-boat gets
enough running for wear of the injection system to become a problem. I very
much doubt that the injector spring might get "worn out".

If, for example, the engine had been left out of action with the injector
pump's fuel connections undone, it could suffer from some corrosion which
could cause it to seize (the clearances are minute) so perhaps when the
tappet has pushed the injector pump's piston, the return spring is unable
to return it to its seat. A fault such as this would probably require
(expensive) attention from a Bosch agent. But I haven't had such a problem
reported.

Have you checked whether part of the "winterizing" done by the previous
owner might have included sealing up the air intake? Just a silly
question...

================

The reply quoted above forgot to mention two other possibilities-

If there's a lack of compression, it could be caused by a crack or leak in
the head or the block- a very serious business.

A check should be made that the fluid entering the injector pump is indeed
pure fuel, and that it hasn't been contaminated with water.

If you as readers, have your own suggestions to add on getting an engine
started, please send them to me and I will add them to the fact sheet.


SPARE PARTS AND SERVICE

Although BMW Marine stopped production so many years ago, a remarkably full
selection of spares is still available from Peter Humphris at P H Marine,
Val Wyatt Marina, Wargrave, Berks RG10 8DY, UK,  tel +44 (0)1189 404419,
fax 01188 404890, email peter.ph-marine@talk21.com    He is prepared to
ship abroad. I don't know of any other stock list for BMW Marine in the UK,
and don't think there is one. As you might imagine, in the absence of
competition, parts from P H Marine are rather costly.

For Renault Couach owners, Mr Chapple, at Merlin Marine, 7 Hawthorne
Avenue, Ilfracombe, Devon EX34 9RR, UK, who runs an 8D, advertises
occasionally in Practical Boat Owner, and offers repair services and spare
parts. I haven't used his services, but have spoken to him by phone, and he
says he is quite prepared to handle the BMW version as well. He can take
phone calls after 6pm, or faxes, on +44 (0)1271 863659.

Another source of parts (and presumably where the two referred-to above
obtain most of their own supplies) is the Hatz organization. Although
nowadays, they provide only air-cooled diesels, they claim to maintain a
stock of spares for all their engines, even those no longer made. Hatz
maintains a widespread international network of dealers, and the head
office of Hatz Diesel is-
Motorenfabrik Hatz Gmbh +Co. kG., D-94099 Ruhstorf,  Germany. Their web
site is www.hatz.com and emails go to marketing@hatz.diesel.de
Phone No +49(0)8531 319220, faxes 319418.
There's a UK Hatz office, Hatz GB, Hinckley, Leics. UK, tel +44(0) 1455
611546, fax 611233, emails to hatzgb@discover.co.uk   ,website
www.hatz-greatbritain.co.uk
When I have asked about marine engine parts, the UK Hatz office seem to be
keen to pass me on to P H Marine, but will presumably accept orders for
spares directly if  the Hatz engine type number is quoted. One would need
to be careful to ensure that the Hatz component was an exact equivalent,
and had not been modified in marinisation. I've no direct experience of
dealing with Hatz, and no knowledge of their prices. If any reader has more
information, please let me know.

Owners in North America (and perhaps elsewhere) may like to know about-
Rich Langtry, P.O. Box 565, Keewatin, Ontario, Canada  P0X 1C0
Tel: 1 807 543 3003, Fax: 1 807 543 2528, e-mail rich@bmwmarine.net
website http://www.bmwmarine.net

This is a venture that aims to provide BMW
Marine owners with spares, information, and service, though I think it's
fair to say that so far the concentration has been on BMW's big
multicylinder petrol engines. Rich is very keen to build up the D7/D12 side
of the business, and is thinking about ways of overcoming the alternator
problem.

In the US, the only provider of parts and service known to me is Kevin Green, at
BMW Marine Service, 2005 Clement Avenue, Building No 9, Alameda, Cal 94501.
He doesn't have email, but his phone number is 510 522 8869 and fax is 510
522 3078. Talking on the phone, he sounds very knowledgeable and
experienced about these engines.

If you're looking for secondhand parts for D7 or D12, you could try Graeme
Williams at Performance Imports Ltd in New Zealand, details given above
under "Gearbox". I found him knowledgeable and helpful.

If you have had dealings with any of the businesses mentioned above, I
would be interested to hear reports, good or bad. That way we can all
benefit. I should add that my only connection with any of them is as a
customer.

AIR FILTER
These are rather expensive to replace at marine prices. Does anyone know if
these top-hat filters are used for other non-marine purposes, at lower
prices? Are they available from Hatz?

I wonder if the recommended frequent replacement of the air filter is
really necessary? The engine was designed to work in a land environment
such as a building site. Unless you are transiting the Red Sea, or a
similarly dusty  environment, the below-stairs area of a small craft should
be rather dust-free. I make a test for time to time to see if my air filter
needs replacing. I remove the air-filter housing, and just hold the filter
in place. Start the engine and run it up to full throttle, under load,
driving the boat. Then pull the air filter away and note if the engine
speed increases, or smokiness gets less. If it doesn't, the filter doesn't
need changing. Mine hasn't been changed in the last 10 years.

If the air filter ever clogged badly, I doubt it would do a lot of harm to
complete your voyage without it. The noise level would increase somewhat,
however. In a bad case, perhaps the filter might unclog after a wash in
petrol and a blow-out, but don't reinstall it on the engine until ALL the
petrol has evaporated!

Stan Duggan (sunebank@supercity.ns.ca) has rebuilt the air filter on his
D12 to take a different element that's cheaply available, and I'm sure he
would explain if you contact him and ask. (But the air filters on the D7
and D12 are completely different)

FUEL FILTERING
A good fuel filter, with a water drain, is certainly called for. Regular
replacement of the filter element was recommended by the makers. In some
circumstances, where dirty diesel is a risk, this may be good and necessary
advice. But where the engine is an auxiliary that may only use a few
gallons in a season, and if the fuel supply is usually uncontaminated,
perhaps it is overkill. If you drain the bowl from time to time, and
nothing but clean oil appears, do you really need a filter change? I doubt
it. But you should at least carry a spare element, just in case.

I found that a replacement element for the original Purolater filter
supplied was hard-to-find or expensive, so I have changed it for a CAV unit
that is more common in the UK. One fuel filter is much the same as another,
but elements aren't usually interchangeable.

Stan Duggan, a D12 owner from Nova Scotia, suggests replacing the fuel
filter with a Fleetguard FF215, and also puts a Racor water separator in
the line.

It's worthwhile removing the top cap from the fuel lift pump and checking
the nylon gauze filter below it, from time to time. This is often the first
line of defense against contamination.

On my engine, the breather hole of the fuel lift pump allows a small amount
of sump oil to escape, which makes a black mess under the engine, but no
real problem; only nuisance-value. Have others encountered this, and has
anyone fixed it?


WATER PUMP

The BMW engines use a Johnson pump with a neoprene impeller. The drive
shaft from the engine uses two almost-identical lip-seals back to back, one
to prevent oil leaking from the engine, the other to prevent water leaking
from the pump. A number of owners have had repeated failures, or short-life
of the water seal. It has turned out that they (me too) had been supplied,
as replacements, with two identical seals for these two different purposes,
both having a steel garter-spring. For contact with salt-water, it's
essential to use a bronze or stainless spring. For the oil seal, either
would do. Try the spring  with a magnet. For water pump parts, try Aquafax,
on +44 (0)1582 568700. They give efficient  service and good value, and
wouldn't make the error described above.

Ian Hopley (ian@ihopley.freeserve.co.uk) adds that rubber seals for the water pump
can be readily obtained from bearing suppliers such as BSL (Bearing
Services Ltd.) in the UK. A suitable seal is made by GACO, part number DPSM
12247, 24mm outside dia. 12mm inside, 7mm thick. Make sure that the spring
is stainless or bronze.

Ian also points out that the ball races for the water pump are standard
units. Each is a single row angular contact bearing, SKF6001, 28mm outside
dia, 12mm inside, thickness 8mm. and readily available. However, I've had
no reports of any failures in this department.

If, in your installation, the exhaust manifold is near or below sea-level,
you need to take special care. If the boat is left idle for a time with the
cooling-water inlet valve open, then water can siphon through the pump
(which can't be relied on to make a perfect seal when it's stationary), up
through the engine, and out through the exhaust water-injection point into
the exhaust system. It can flood the exhaust system, and may go on to fill
the cylinder and the rest of the engine; perhaps even flood the boat.
Protection is simple, requiring an inverted u-tube to take the cooling
water above sea-level, with a thin tube teed in to it at its highest
point, which passes overboard (to the transom, on my boat). This pipe
provides a tell-tale to show the cooling system is working properly, by a
small jet of water that emerges whenever the engine is running. But, more
important, when the engine stops it allows air to enter and break the
siphon.

SPEED-CONTROL LINKAGE

Several D7 owners have reported loss-of-power or stalling, which has in the
end been attributable to a bad mechanical connection between the speed
lever on the port side of the engine and the threaded shaft that links this
lever to the governor inside the crankcase.

Unfortunately, this connection is made by pinching the lever between two
locknuts on the shaft. In my view, this is a mechanical abortion, of which
BMW should be ashamed. The pinch-nuts can work loose and allow the speed
lever to slip. To fix it, you need a fistful of spanners.

=========================================================
BATTERY-CHARGING MATTERS

An owner in New Hampshire has suffered the usual alternator failure, but
adds that he has fitted instead a solar panel which trickle-charges his
battery all the time. He finds that arrangement is satisfactory, even
though he does quite a lot of night sailing. His latitude will give him
more sunshine than those of us who live in mistier and more Northerly
climes receive (in Old Hampshire, for example). But it's an option worth
considering.

Others with engines suffering from alternator disease have obtained
replacement stators from Rich Langtry (rich@bmwmarine.net) in Canada, at
just $112. This sounds a lot more reasonable than prices I have seen quoted
in Britain. The difference may be enough to pay for email shipping costs.
My only caution about replacing the stator is this: somehow I doubt whether
the basic design has been improved, and I suspect that a replacement is
likely to fail in the same way as its predecessor. I think the culprit is
ingress of damp into the insulation of the control windings..

Another source, for a stator, at a similar price, is-
Kevin Green, at BMW Marine Service, 2005 Clement Avenue, Building No 9,
Alameda, Cal 94501. He doesn't have email, but his phone number is 510 522
8869 and fax is 510 522 3078.

An Aside... For those that are importing any equipment from outside the EEC
to fit to their boats, they ought to be able to claim exemption from duty
and VAT under "ship work" provisions. These were presumably intended to
apply to commercial vessels but there seems to be nothing preventing us
small craft owners from taking advantage of these rules. I have successfully
avoided any such payments when importing a marine gearbox into UK from New
Zealand (but it required a bit of arguing).

A D7 owner in the UK, who happens also to run a garage business, has just
taken his engine out to install a vee-belt drive to a car alternator,
placed just aft of the cylinder. The belt will emerge through the
(enlarged) ventilation slot just above the flywheel, which is revealed when
you remove the old electrics. A disc, with a central hole, will be attached
to the flywheel, in place of the fan ring, and this will carry the drive
pulley. He promises further details when he has tried this scheme out. In
many ways this is similar to the scheme I adopted 5 years ago, but the
proposed mounting of the drive pulley is quite different, and possibly much
simpler.

I have some news to report on my own scheme for driving a car alternator,
in a similar way to that described above. I pointed out that its big defect
was this- because the belt drive emerged from a slot in the bell housing,
behind the engine, if the belt ever failed it might be necessary to part
engine and gearbox to replace it. But to avoid that job I had invested in a
special vee-belt made up of detachable links, which could be parted, put
into place, and linked together again.

Well, after 5 years or so, the old rubber vee-belt finally gave up last
week, so I have had to fit that link-belt in its place, and have done the
job without removing the engine. It was a reasonably smooth operation, and
the new belt seems to be working well. I thought it might be much more
noisy than an ordinary vee-belt, but that doesn't seem to be the case: not
compared with the racket that the engine makes, anyway. How long it will
last, I can't tell, but the makers insist that it should have a much longer
life than a standard belt. We shall see.

For anyone that's interested, the belt I fitted went by the odd name of
"Nu-T-Link", and is available in the UK from branches of BSL, the bearing
suppliers. The belt type is Z/10, the smallest belt that's available, 10mm
wide and about 15mm pitch. It is sold by the metre (which is more than you
will need) at about £15. They are produced by BTL in the UK, email
btl@fenner.com

If that detachable belt proves satisfactory long-term, then it disposes
with the big snag of my alternator drive scheme, as there's no longer any
need for dismantling when changing belts.

======================================

WHAT ON EARTH IS THE "IMPULSE GENERATOR"?

Two owners have reported failure of the "red light" indication which
resulted in the need to renew the object, curiously named "impulse
generator", which goes between the regulator and the fuse to the battery.
From my own engine, I threw out all these components years ago when I
fitted the car-alternator. But it intrigues me rather, what there is in
that little box. Does anyone know? Can anyone make a guess?

My suspicion is that it may simply be a small relay, energized by a few
turns of heavy wire carrying the output current to the battery, which then
breaks a contact. This contact connects the charge-indicator lamp to
ground. If I am right, then if the item failed you could get going again by
removing it and shorting the power-in lead to the power-out lead. All you
would lose would be the red-lamp indication. Does this make sense? Has
anyone opened up that little box?


GETTING INFORMATION.

A copy of the D7 Owners' Manual (which is NOT a repair manual) has been
made available by David Pierce, at
www.geocities.com/NapaValley/7292/bmwd7.htm.

BMW Marine produced an informative parts-list booklet, covering both D7 and
D12. This shows useful exploded diagrams of the various parts of the
engine. Ian Hopley (ian@ihopley.freeserve.co.uk) has a copy of this parts list, and
kindly offers to provide a copy of the relevant part. But please specify
which bit of the engine you need to see, and whether it's D7 or D12, to
minimize the number of pages needed.

IN SUMMARY

This note has concentrated on the problems that can occur with the D7
engine. However, my own experience, and that of many owners, is that except
for the charging-system problems, ownership has been remarkably
trouble-free. In 21 years, the engine has not let me down, except on one
occasion when the primary fuel filter (within the tank) gunged up (hardly
the engine's fault). Now, with its rebuilt alternator drive, I wouldn't be
without my little engine.

SOME VITAL STATISTICS

BMW D7 Single-cylinder diesel, power output 7 HP at 3600 RPM (6 HP to shaft)
Total Weight 68 kg (150 lb)
Overhead valves, pushrod actuated, splash lubrication, raw water cooling.
Renault RC 8D is similar but 83 kg weight.

MAKING CONTACT

Over the last couple of years, D7 owners, spread around the world, have
contacted me, many as a result of references by Pat Manley on the Practical
Boat Owner website <www.pbo.co.uk>  I've been able to pass on some tips,
and have learned a lot also. For anyone that needs to know more, or would
just like to chat about their D7, or pass on their own findings, I am happy
to be contacted. Preferably by e-mail to george@huxtable.u-net.com or by
phone or fax to +44 (0)1865 820222, otherwise mail to George Huxtable, 1
Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

If any errors in this fact sheet are uncovered, or if there are comments to
add, please don't hesitate to get in touch.

My hope is that we might create an unofficial "owners' club", with no
subscription.

Finally, I have to state that all the information is provided in good
faith, from one owner to another, with as much accuracy as possible, but no
liability is accepted for any errors that  might exist.

George Huxtable.

Some boats that use the BMW D7 or D12 : (send in your own links)

S2 7.9   Aloha 27    Wavelength 30

Current News and Feedback from Owners:

Greetings to D7 /D12 users and old friends, at the start of another boating season
(for those in the Northern hemisphere).

I've had a call from Charles Garrod, at charles.garrod@btinternet.com, who
lives in Brixham, Devon, UK (lucky fellow).

He has suffered the usual corrosion failure of the exhaust elbow on his D7,
and is looking for a replacement. If there's a discarded D7 engine within
his reach, that could be dismantled for spares, and has an exhaust elbow
that's reasonably intact, he would be most interested. Contact him
directly.

If anyone has experience of fabricating such an elbow, or adapting
something from another engine, many owners would be interested.

If any owners of abandoned engines are looking for a buyer at reasonable
price, if you pass details to me, with information on location, I will pass
it around.

==================

 New source of BMW marine parts for the D7 & D12 in the USA,
 Sealand Power Industries, Inc. Linden, New Jersey

tel: 1-800-225-0004 {908}486-7600 fax: 1-908-486-1056

======================
======================

A message from Rich Langtry, in Lake of the Woods, Ontario, Canada, tells
me that in the new year he expects to be able to offer a solution to the
alternator stator problem that has affected nearly every D7 and D12. He has
stocks, new or used, of nearly every component of these engines, including
stators of the existing design. He has supplied rebuilt engines.

Rich Langtry

V12 Engineering

Tel:| +807 543 3003
Fax:| +807 543 2528
rich@bmwmarine.net    or website    www.bmwmarine.net

ANY IDEAS ABOUT THESE PROBLEMS?

Two D7 owners, both in the US, report similar problems. Do the following
symptoms sound familiar to anyone else? Does anyone have suggestions for
tackling them? Any ideas that are sent to me will be passed on. Your e-mail
address will be passed on only if you specifically authorize it.

After his engine has undergone a complete overhaul, a D7 owner in Florida
reports problems. He can start it only when the start button has been
pulled out until it clicks (and this in a Florida summer!). His engine will
run well at full throttle, giving him 6 knots, but stalls when he tries to
throttle back. As a result, when returning to his berth, he has to cut his
engine when well off, judging the distance so that he has lost most of his
way as he reaches the pontoon. A dodgy business, indeed.

Another American owner says-

"As you know, there is a knob next to the fuel pump which is
meant to be pulled out to aid in cold starts. For whatever reason, when I
pull it out it lock the engine so that it will not turn. The knob also won't
push back in at that point and I have to jiggle and coax it until it final
retreats. When I first bought the boat I thought I had seized the engine!
Any thoughts on what is wrong?"

To me, this sounds a serious business that needs to be fixed. Has anyone
else met it or can anyone suggest how to fix it?

Glowplugs ?

Has anyone tried replacing the starting paper holder on a D12 with a glow plug?

Yes!

"A couple of seasons ago we had starting problems in cold weather and rather than use "easy start" I tried drilling the centre out of a starting paper holder and tapping it to take a Peugeot glow plug (first one I laid hands on). I connected a 12v feed straight to it but unfortunately, it didn't make a blind bit of difference! I was a bit surprised at this but maybe its because of the location of the glow plug and the amount it projected into the pre-combustion chamber. In order to sort it out I had to take the head off and when I did so, I found the valves were leaking. Once I'd ground them back in it was fine so I gave up on the glow plug!" Ian Hopley ian@ihopley.freeserve.co.uk
 

I've just had an email from Ian Hopley, who is mentioned in the context of
getting a belt drive from his starting-handle shaft to an alternator (and
maybe elsewhere). 

"I got fed up with all the rubber dust generated round my alternator by the
"poly-V" belt on my alternator installation so I tried going over to a
toothed belt (a miniature timing belt) the season before last.
Unfortunately, this has resulted in me snapping about 2 belts per season!
This year (if I ever get back in the water!) I'm going to try a slightly
larger driven pulley on the alternator (about 1.25" instead of 1").

I'll let you know how it goes!"

ian@ihopley.freeserve.co.uk

=======================================================


My D7, now 25 years old, has started and run OK after the Winter lay-up.
which makes me a happy man...

However, I had some problems back in January, when I tried a midwinter
start on a really cold day, and with a battery that was less than 100%.
Even helped by some arm-exercise on the starting handle, I couldn't get it
to even cough. But then, I pushed down the button on the inlet manifold,
that injects a thimble-full of fuel through the inlet valve, while the
engine was spinning, and it fired straightaway. That was the first time
I've had to use that little gadget in anger, and was pleased how well it
worked. No doubt the extra oil helps to seal the valve seats and the rings,
and perhaps boosts the compression ratio a bit.

That starting problem may have been the first sign of reduced compression
in my engine, which has had the top off only once in its long life.

Hope your own engines are doing as well.

George.
 

TO BECOME A MEMBER OF THE BMW MARINE ENGINE GROUP:

1) Go to the Yahoo! Groups site by clicking on this link:


http://login.yahoo.com/config/login?.intl=us&.src=ygrp&.done=http%3a//groups.yahoo.com%2Fgroup%2Fbmwmarineengines%2Fjoin%3F
 

(If clicking doesn't work, "Cut" and "Paste" the line above into your
   Web browser's address bar.)

-
replace the email address in the box with your own!

================================================================
contact George Huxtable by email at george@huxtable.u-net.com, by phone at
01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
================================================================

The BMW logo is symbolic of a white propeller blade, against a blue sky. It reflects the origins of BMW as a maker of military aircraft engines during the first world war.

BUY or SELL

BMW D7 & D12 Marine Engines and Parts

Anyone with parts or whole engines that they would like to swap, barter or sell? just list actual condition, a fair price and a way to make contact, and we'll post for the group to consider.
 

Posted Sept 30th 2005

Hi, I am selling my D7, I need more H.P. it is installed on my Aloha 27
and it is running ok. If it does not sell I am going to remove it from the boat
and tune it up over the winter, I bought the boat last Fall, it is an 1984 boat,
Thanks.
PATRICK T. MEALIFFE
PROGRAM INSTRUCTOR
TRADES COUNCIL & T.D.S.B.
DESIGN & CONSTRUCTION
DIVISION
OFFICE # 416-395-2039
FAX # 416-395-2042

Contact Webmaster : alibiwavelength30@yahoo.ca