I have a 20hp Bukh
in my ship, with a PSS seal. Although the engine
is at least 20 years old, service
and upgrading of parts
is up to date. Hitherto running like a sewing machine
, but on going back into the water
after a couple of weeks on the hard
, at mid-revs a penetrating squeal emerged, only to disappear as I dropped the revs.
I have tried:
<replacing the alternator
belt, from which I've had a similar noise
in the past caused by slippage
<Running under load without alternator
belt - same noise
<replacing transmission oil
<checking and cleaning
bellows and mating faces on PSS, no problems with dry running
<Diving down and checking on propeller
shaft anode - no problems, not loose.
unloaded through entire rev range - no problem, no noise.
My boat is steel
and resonates any such noise so that it's impossible to pinpoint the location of the sound source, but I suspect it is from the gearbox
aft. Would it be possible that it could come from the shaft bearing aft of the seal?
The noise creeps in as I increase revs, and likewise dies down as I reduce. It is very loud and piercing, not especially high pitched, and most like the sound of a slipping alternator belt.
At all other times I have loved and understood the engine.
Any clues would be much appreciated - Thanks!