Strange engine behavior. Any ideas?

[waterant]

Hi guys,

I'm puzzled by something strange happening to my Westerbeke W21 (1986) engine yesterday. First time like this in 3 years I used it (I run engine every weekend for several hours, change oil every year or around 100 hours).
In the morning, I started an engine, it was running for 5 hours as usual - fair vibration on 800 RPM, some vibration at 1500 RPM and more or less smooth at 2200 RPM. I stopped an engine for 2 hours.
Started it again after 2 hours and it started running smooth as butter - no vibration at all - tachometer went crazy - it showed 1500 RPM on lowest gas setting, and went up to 4000 RPM as I added more gas (not even maximum setting) but I did not feel it was running that fast (max RMP for this engine is 3000RPM and you know it's at maximum if you go to this limit), just running very smooth.
I run it like this for 1-2 min but it did not feel right. I'd be glad to have engine running that smooth but it's probably a wishful thinking for 1986 diesel.
I started it again, it did this again. I stopped it for 5 min or so, started again and it was normal for the rest of the trip (2-3 hours).

any ideas what this can be?

Thanks,

Anton

 

[macnorton]

If the engine has electronic stop (no pull to stop handle), it could be the stop soleniod not opening fully because of an electrical problem, that is the only way you could get these combined intermittent problems that I can think of.
This is just as stab in the dark as I have never heard of this one before?

Do post the reason on here when you trace the problem.

 

[Hypocacculus]

Prop fallen off?

 

[waterant]

Prop fallen off?

that would be fun, but no, on third attempt everything start working as before and we finished the trip (another 2 hours to destination) without any problems. and that behavior was there without engaging a gear at all so i do not think this is something with transmission or prop.

If the engine has electronic stop (no pull to stop handle), it could be the stop soleniod not opening fully because of an electrical problem, that is the only way you could get these combined intermittent problems that I can think of. This is just as stab in the dark as I have never heard of this one before?

I have "pull to stop" handle. It was pushed all the way in as always for normal operation (i pull to stop).
maybe it was really running as fast as tachometer indicated and that's why it was so smooth? I see this as the most likely explanation but what can cause a diesel to run that fast?

 

[macnorton]

Slipping gearbox, drive plate, coupling, is it a Hurth gearbox?

you did say you felt the tacho was mis-reading so assumed electrical.

 

[mtb]

how hot was the air temp

 

[omega2]

Is all this running under load or in your berth??

 

[Bilgediver]

Hi guys,

I'm puzzled by something strange happening to my Westerbeke W21 (1986) engine yesterday. First time like this in 3 years I used it (I run engine every weekend for several hours, change oil every year or around 100 hours).
In the morning, I started an engine, it was running for 5 hours as usual - fair vibration on 800 RPM, some vibration at 1500 RPM and more or less smooth at 2200 RPM. I stopped an engine for 2 hours.

Anton

It is possible you have two faults here. The rough running could be one of two things. It sounds like one cylinder may be playing up and this could be either
faulty injection or boorderline low compression.

The engine may only be running on two cylinders at low revs especially when cold and then as the revs increase the third cylinder decides to join in.

One easy thing to do is to check the compression of the three cylinders.This is done by removing the injectors and putting a compression gauge in the injector pocket. I would also get all three injectors serviced at a diesel shop.

Your second fault of unexplained high speed running on low gas setting needs more investigation as you seem unsure whether the engine really was running fast.

 

[PCUK]

A cheap strobe tacho will confirm true engine revs as a starting point.