Perkins 92b shuddering issue

[DBA Forum (B) - Cathy Lee]

Hi all

My engine is driving me mad and I don't what else to try.
When cold it worked perfectly at low revs (850) in all gears. Once hot it shudders and vibrates in all gears making it very difficult to manoeuvre at low speed.
I have tried everything - including 2 marine engineers looking at it.
It's not the engine mounts, the valves are fine and the fuel injectors appear fine (only inspected in situ though).
The revs are set right and I certainly don't want to up them or the barge will go too fast when manoeuvring in right spaces.
Any suggestions? ....

It's driving me mad.

Best wishes
Cathy

[DBA Forum (B) - Richard Cooper]

Does it rev freely in neutral from tickover up to normal revs? water or muck in the filters can cause some very lumpy running.

[DBA Forum (B) - Cathy Lee]

Even in neutral, when warm, I can't leave it in tick off without major shuddering - have to increase the revs to 1000.
Just changed all filters and had engine service

Post by DBA Forum (B) - Richard Cooper
Does it rev freely in neutral from tickover up to normal revs? water or muck in the filters can cause some very lumpy running.

[DBA Forum (B) - Colin Stone]

Cathy,

Worn flywheel dampers? When cold stay reasonable rigid. When hot are too soft and allow resonance at idle.

A bit of a job to replace and R&D do a thriving trade in better replacements than OEM supply.


Colin Stone
KEI
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[DBA Forum (B) - Cathy Lee]

Hi Colin

I haven't even heard of a "flywheel damper" - didn't know there was such a thing.

The shuddering problem has been there as long as I can remember from newish. For that reason I don't think it's anything that's worn.
Maybe it's something I am gonna have to live with ...

Cathy

Post by DBA Forum (B) - Colin Stone
Cathy,
Worn flywheel dampers? When cold stay reasonable rigid. When hot are too soft and allow resonance at idle.
A bit of a job to replace and R&D do a thriving trade in better replacements than OEM supply.
Colin Stone
KEI
Sent via BlackBerry® BIS

[DBA Forum (B) - Colin Stone]

Cathy,

Well, it should not being doing it!

Perhaps it has been not brilliant since since new?

Have a look here:
www.randdmarine.com/mdamper.asp

Regards,
Colin
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[DBA Forum (B) - Colin Stone]

Hi Cathy again,

Also, the engine/gearbox may not even have a damper at all - which would explain your experience since new.

Ask the boatyard/builder/installer or Perkins if a damper is fitted.

Regards,
Colin
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[DBA Forum (B) - Richard Cooper]

Has it got rubber mounts? its quite a big 4 cyl engine and is more than 1 litre per cyl so is likely to be trying to exit the boat every time it fires, I admit I am not too knowlegable about them but if it is quite high on its mounting feet it could cause this. If it all seems ok and its not perched up on the top of its mounts I would honestly think about fixing a car shock absorber to some heavy bit of the thing and to a hefty bit of hull, all sheer speculation of course but if its been like it since new its likely to be something to do with how its held in place.

[DBA Forum (B) - Colin Stone]

Doubt if it is engine mounts. I've run my engine, 6 cyl 8 ltr, when new just sat on wooden packing pallet. Perfectly smooth. As it happens at idle, when no real torque is being generated to twist against the mounts, suggests to me that it is in the transmission.

Several diesel cars have dual mass flywheels, which have rubber damping in their construction, and are expensive to replace. If a single mass flywheel, no rubber, is fitted the engine shudders at idle.

And of course engine mounts should be sized for both the proportion of engine and gearbox weight on each mounting and the engine torque for ahead and astern.

Colin Stone
KEI
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[DBA Forum (B) - Richard Cooper]

I started an ancient Ailsa Craig 2 cyl on a pallet, I had to chase it across the car park to stop it.

[DBA Forum (B) - Colin Stone]

I started an ancient Ailsa Craig......

Well, yes - ancient being the operative word. I think modern engines run a little more smoothly.

Colin Stone
KEI
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