I have an 8KW Westerbeke diesel generator (about 12 years old) which
has an odd vibration issue at times. This happens most often under
moderate to heavy load and lasts for 15 to 20 seconds at a time. The
vibration is so violent that the guages are impossible to read and it
shakes the entire boat. Vital signs like temperature and oil pressure
look normal, there is no exhaust smoke, and other than the vibration
episodes, it starts and runs very well. There is ample raw water flow
and the electrical specs for voltage and frequency check out OK.
I hate to replace it if there is a simple fix.

Anyone have an idea what the problem could be?

On Friday 03 September 2004 3:48 am in rec.boats.building Wayne.B wrote:

I have an 8KW Westerbeke diesel generator (about 12 years old) which
has an odd vibration issue at times. This happens most often under
moderate to heavy load and lasts for 15 to 20 seconds at a time. The
vibration is so violent that the guages are impossible to read and it
shakes the entire boat. Vital signs like temperature and oil pressure
look normal, there is no exhaust smoke, and other than the vibration
episodes, it starts and runs very well. There is ample raw water flow
and the electrical specs for voltage and frequency check out OK.
I hate to replace it if there is a simple fix.

Anyone have an idea what the problem could be?

This is typical of an intermittent overload.

I would suspect a faulty electric motor starting somewhere
pulling a very heavy starting current. Try disconnecting
fridges, aircons, bilge pumps, etc and see if the problem
goes away. Anything with an electric motor which starts
and stops automatically.
It is probably a good idea to check all of the fuses to
see if someone has "fixed" a problem by replacing a fuse
with a larger rating or even a piece of wire/nail.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

On Fri, 03 Sep 2004 12:02:46 +0100, Chris Newport
wrote:
This is typical of an intermittent overload.

I would suspect a faulty electric motor starting somewhere
pulling a very heavy starting current.

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

I guess it's a possibility but is not showing up on the panel meters
as far as I can see. My air conditioning compressors and the
circulation pump all have high starting loads but they were running
steady state at the time.

On Friday 03 September 2004 4:17 pm in rec.boats.electronics Wayne.B wrote:

On Fri, 03 Sep 2004 12:02:46 +0100, Chris Newport
wrote:
This is typical of an intermittent overload.

I would suspect a faulty electric motor starting somewhere
pulling a very heavy starting current.

I guess it's a possibility but is not showing up on the panel meters
as far as I can see. My air conditioning compressors and the
circulation pump all have high starting loads but they were running
steady state at the time.

You need to be very lucky to actually be looking at the
meters when the problem happens, so you best chance is
to start disconnecting things until the problem goes away.

If the meters are _definitely_ not showing an overload
then something must be wrong in the generator.
An intermittent short inside the generator or before
the meters is possible, as is some idiot wiring something
in before the meters.

Mechanically this could also be due to an intermittent
blockage to one of the injectors.
A valve sticking open is also a less likely possibility,
take off the valve covers and check for broken or damaged
valve springs.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

Make sure the unit is fused or has a breaker in the output.
Is it possible some of the mounts, mountings bolts, engine bolts are loose,
broken or missing?

"Chris Newport" wrote in message
news:9196199.SVREgKCQlk@callisto...
On Friday 03 September 2004 3:48 am in rec.boats.building Wayne.B wrote:

I have an 8KW Westerbeke diesel generator (about 12 years old) which
has an odd vibration issue at times. This happens most often under
moderate to heavy load and lasts for 15 to 20 seconds at a time. The
vibration is so violent that the guages are impossible to read and it
shakes the entire boat. Vital signs like temperature and oil pressure
look normal, there is no exhaust smoke, and other than the vibration
episodes, it starts and runs very well. There is ample raw water flow
and the electrical specs for voltage and frequency check out OK.
I hate to replace it if there is a simple fix.

Anyone have an idea what the problem could be?

This is typical of an intermittent overload.

I would suspect a faulty electric motor starting somewhere
pulling a very heavy starting current. Try disconnecting
fridges, aircons, bilge pumps, etc and see if the problem
goes away. Anything with an electric motor which starts
and stops automatically.
It is probably a good idea to check all of the fuses to
see if someone has "fixed" a problem by replacing a fuse
with a larger rating or even a piece of wire/nail.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

you can test it by adding large non-sensitive cheap loads to the unit.
(By non-sensitive cheap loads I refer to large home power tools, large
lights, etc.) Add the resistive loads first (lights etc)and then fire
off a couple inductive load items (motors). If it is 220, try both
sides independently. I would not do this test with your expensive
compressors etc. 110V boat lights are not a problem. You can't hurt an
incandescent light with brown power.





scott downey wrote:
Make sure the unit is fused or has a breaker in the output.
Is it possible some of the mounts, mountings bolts, engine bolts are loose,
broken or missing?

"Chris Newport" wrote in message
news:9196199.SVREgKCQlk@callisto...

On Friday 03 September 2004 3:48 am in rec.boats.building Wayne.B wrote:


I have an 8KW Westerbeke diesel generator (about 12 years old) which
has an odd vibration issue at times. This happens most often under
moderate to heavy load and lasts for 15 to 20 seconds at a time. The
vibration is so violent that the guages are impossible to read and it
shakes the entire boat. Vital signs like temperature and oil pressure
look normal, there is no exhaust smoke, and other than the vibration
episodes, it starts and runs very well. There is ample raw water flow
and the electrical specs for voltage and frequency check out OK.
I hate to replace it if there is a simple fix.

Anyone have an idea what the problem could be?

This is typical of an intermittent overload.

I would suspect a faulty electric motor starting somewhere
pulling a very heavy starting current. Try disconnecting
fridges, aircons, bilge pumps, etc and see if the problem
goes away. Anything with an electric motor which starts
and stops automatically.
It is probably a good idea to check all of the fuses to
see if someone has "fixed" a problem by replacing a fuse
with a larger rating or even a piece of wire/nail.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

you can test it by adding large non-sensitive cheap loads to the unit.
(By non-sensitive cheap loads I refer to large home power tools, large
lights, etc.) Add the resistive loads first (lights etc)and then fire
off a couple inductive load items (motors). If it is 220, try both
sides independently. I would not do this test with your expensive
compressors etc. 110V boat lights are not a problem. You can't hurt an
incandescent light with brown power.





scott downey wrote:
Make sure the unit is fused or has a breaker in the output.
Is it possible some of the mounts, mountings bolts, engine bolts are loose,
broken or missing?

"Chris Newport" wrote in message
news:9196199.SVREgKCQlk@callisto...

On Friday 03 September 2004 3:48 am in rec.boats.building Wayne.B wrote:


I have an 8KW Westerbeke diesel generator (about 12 years old) which
has an odd vibration issue at times. This happens most often under
moderate to heavy load and lasts for 15 to 20 seconds at a time. The
vibration is so violent that the guages are impossible to read and it
shakes the entire boat. Vital signs like temperature and oil pressure
look normal, there is no exhaust smoke, and other than the vibration
episodes, it starts and runs very well. There is ample raw water flow
and the electrical specs for voltage and frequency check out OK.
I hate to replace it if there is a simple fix.

Anyone have an idea what the problem could be?

This is typical of an intermittent overload.

I would suspect a faulty electric motor starting somewhere
pulling a very heavy starting current. Try disconnecting
fridges, aircons, bilge pumps, etc and see if the problem
goes away. Anything with an electric motor which starts
and stops automatically.
It is probably a good idea to check all of the fuses to
see if someone has "fixed" a problem by replacing a fuse
with a larger rating or even a piece of wire/nail.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

Wayne,
My guess is that it is not electrical. I think your flex plate drive is
either loose or worn out. The alternator has bearings only on the outboard
end. The engine rear main bearing acts as the other armature bearing. This
mechanical connection is usually done through a flex plate which is bolted
to the engine flywheel and a splined hub drives the armature or rotor. To
check this, the alternator must be removed from the engine.
Steve

"Wayne.B" wrote in message
...
I have an 8KW Westerbeke diesel generator (about 12 years old) which
has an odd vibration issue at times. This happens most often under
moderate to heavy load and lasts for 15 to 20 seconds at a time. The
vibration is so violent that the guages are impossible to read and it
shakes the entire boat. Vital signs like temperature and oil pressure
look normal, there is no exhaust smoke, and other than the vibration
episodes, it starts and runs very well. There is ample raw water flow
and the electrical specs for voltage and frequency check out OK.
I hate to replace it if there is a simple fix.

Anyone have an idea what the problem could be?

On Sun, 5 Sep 2004 09:49:03 +0200, "Steve Lusardi"
wrote:
My guess is that it is not electrical. I think your flex plate drive is
either loose or worn out. The alternator has bearings only on the outboard
end. The engine rear main bearing acts as the other armature bearing. This
mechanical connection is usually done through a flex plate which is bolted
to the engine flywheel and a splined hub drives the armature or rotor. To
check this, the alternator must be removed from the engine.

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

Thanks, your assessment of not being electrical jibes with my
observations. What would explain the intermittent nature of the
vibration given a more or less constant electrical load? Is the flex
plate a coupling with a rubber hub?

I would think that it is just simply a resonance factor.
Ever heard one of those old Cummins 160's?
Let them idle & they are as quiet & smooth as a church mouse. Increase the
revs very slowly & you'll find that at 1400, 1600, 1800 & 2000 revs they
just about shake out of the chasis. (truck)
Most diesels do it to a certain extent. Next time it does it, try adjusting
your governer up or down a few revs & see how it goes.
My guess is that under that certain load, it hits the "rattle" speed.
Maybe if you can tweak it a weeny bit, it might not come down to that rattle
speed under load?
BruceM


"Wayne.B" wrote in message
...
On Sun, 5 Sep 2004 09:49:03 +0200, "Steve Lusardi"
wrote:
My guess is that it is not electrical. I think your flex plate drive is
either loose or worn out. The alternator has bearings only on the
outboard
end. The engine rear main bearing acts as the other armature bearing.
This
mechanical connection is usually done through a flex plate which is
bolted
to the engine flywheel and a splined hub drives the armature or rotor. To
check this, the alternator must be removed from the engine.

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

Thanks, your assessment of not being electrical jibes with my
observations. What would explain the intermittent nature of the
vibration given a more or less constant electrical load? Is the flex
plate a coupling with a rubber hub?