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

[Jim Sweet]

Bruce,

You have described , almost verbatim, a problem that we have had since late 
last year.  The only differences are that the knocking doesn't sound like it 
occurs with every turn of the shaft because it only seems to happen  at 
1900-2000 rpm in a hard port turn.  The knocking  sounds like someone is 
tapping the hull with a rubber hammer possibly in the aft lazerette.  I had 
the boat pulled and the marina couldn't find anything and suggested that the 
very minor play in the rudder meant that the bearings needed replacing. 
Didn't feel right so I declined the service.  I have crawled around in the 
lazerettes and can't find anything loose and I plan on pulling EVERYTHING 
out of the storage areas to see if there is something loose.  I even checked 
the aft water tank to see if there was any play in that.  Someone suggested 
the transmission but I was below with She Who Must Be Obeyed driving to 
produce the noise and it didn't seem to be anywhere near the tranny or shaft 
coupling.  Even my gearhead friends are stumped.  If anyone finds a solution 
or what the problem is please post it.  Thanks.

Jim Sweet
TGIF (Thank God It Floats) 902


----- Original Message ----- 
From: "B. Stumpp" <bstumpp at comcast.net>
To: <c320-list at lists.catalina320.com>
Sent: Sunday, May 10, 2015 4:40 PM
Subject: [C320-list] Knock, knock, who's there?


> 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?
>
>
>
> Bruce Stumpp
>
> Adventure, #647
>
> Frog Mortar Creek, Maryland
>
>
>