High pitch whine.

[highportsail]

I have a 02 420 and I know exactly what you are talking about. I know it must be the marine gear as it does not do it in neutral. I have been redoing the soundproofing in engine room and generator as well as paint the under side of cockpit floor with sound absorbing paint. I still notice it a little but not much. I can run the engine at it’s sweet spot around 3100 rpm without all the racket.
Not sure exactly the cause is but think it is the cutlass .

 

[splax]

I think it might be lubrication related. Do you need to change the transmission oil or lube the turbo bearings?

 

[Don Lucas]

Thanks for the reply, will talk with the mechanic about the turbo, the wife is another issue!

Why???? If you have to talk to your "mechanic" about it you need a new mechanic!

 

[SG]

1951seayalater (who posted the original issue), said he didn't believe that the noise was from within the engine compartment.

If you have a squealing transmission or turbo, I suspect that his belief would have been different.

 

[uncledom]

It could be the turbo and your hearing through the exhaust rather than in the compartment.

 

[Skipper]

It could be the turbo and your hearing through the exhaust rather than in the compartment.

Also his previous perception "in the engine compartment" could be related to where his ears were. That is, if he's listening at the front of the engine, and the trans and turbo are in the back, the noise interference from a running diesel could be a factor.
BTW this is a 2-month-old thread someone dug up. The OP could have a different boat by now.

 

[SG]

It could be the turbo and your hearing through the exhaust rather than in the compartment.

I'm not sure how? Can you explain that. I don't understand how a turbo with a bad bearing isn't "connected" acoustically in through the cylinders to send the noise through the cylinders, valves, hydra-lift muffler, and back.

Also, it's episodic at certain RPM's (and not in reverse)?

 

[uncledom]

It is in the exhaust system, perhaps you just don’t hear above the clacking when your in the engine box?

BTW this is a 2-month-old thread someone dug up. The OP could have a different boat by now.

Perhaps we should be looking for the new owner.

 

[splax]

If it is a harmonic resulting from poor lubrication to a bearing or transmission gear, it might transmit through the shaft through-hull bearing foundation to the cockpit sole. The engine mass might dampen the vibration or other noise drown out the whine in the cabin.