[C320-list] Knock, knock, who's there?

[B. Stumpp]

Back in May I posted the following on the forum: 

 

"We went out for our first Spring sail this afternoon.  Everything worked 
great BUT with the engine running and turning left I get a knocking sound 
with what seems like every revolution of the prop shaft.  It does not make 
the noise when going straight, turning right or in either direction in 
reverse.     If I speed up the engine the noise  goes faster.  I stuck my 
head in the engine compartment both in front of and behind the bulkhead, 
the sound is emanating farther back towards the stern.  It's not  a real 
loud knock but kind of like someone lightly tapping on the deck with a 
hammer as a surveyor does when checking for moisture.   Before we launched 
the cutlass bearing and strut all seemed fine.  Has anyone experienced this 
before?" 

Following is the best I can offer right now on a cause and a plan going
forward: 

 

Nothing totally conclusive on the cause of the knocking but we think it was
wear in the cutlass bearing.  I had the engine aligned and it seemed to
occasionally make the noise but it was not as bad as it had been.  We hauled
the boat  - service hang on the crane straps - and there was some looseness
in the bearing but not too bad.  Decision by the mechanic, marina service
manager and myself was it was not bad enough to fix right then and there so
we relaunched and have been using it over the summer.  Have not really heard
the noise since so am thinking the realignment helped but the bearing needs
to be addressed.  Plan is to replace the cutlass bearing and change to a
stainless shaft over the off-season.         

Bruce Stumpp 
Adventure, #647 
Frog Mortar Creek, Maryland