Here is a thought, one time we had a mishap that resulted in the rudder 
starting to delaminate and for the first bit of the journey home we had a 
similar type of unexplained noise, thunk or what ever. Turned out that the 
rudder was delaminating more and faster than I thought and one skin was 
essentially delaminated but still attached at the top.  Eventually the noise 
went away but when we got into port I realised the entire skin had detached 
from one side of the rudder.  If you have the boat out for the repairs have a 
good look at the rudder for delamination.

Cheers,

Tom S

From: Bruce Whitmore via CnC-List 
Sent: Wednesday, July 29, 2020 6:13 PM
To: C&C List 
Cc: Bruce Whitmore 
Subject: Stus-List Unidentified clunk when motoring - 1995 C&C 37/40+

Hello all,

While we were moving our boat to the yard to get it repaired (see my previous 
post about a jetski hitting us), we motored about 12 miles.  For reasons I can 
get into later, we were going only about 4 knots.  We were in the Gulf of 
Mexico and the going up Tampa Bay in light conditions with relatively minimal 
seas.  About every 30 or 45 seconds, without any particular connection to 
waves, we got a quiet but discernible "thump" or "thunk" that I could feel 
through my feet.  It seemed to be most noticeable when I propped my foot on the 
starboard stern locker.  That is the propane locker.  I looked in there, and 
did not see the tank rocking or other reason for the noise.  


It did not seem to be linked to waves, as we hit multiple rocking boat wakes 
and other wave forms, so I saw no consistency there.  Nor did I see any link to 
revving the engine, shifting in & out of gear, etc.  


There was no indication of a crab pot bouy or anything else, either, but I 
haven't been under the boat.  


Any idea what might be causing the noise?

Would a failing motor mount cause this, and how would I diagnose it?

Thanks for your insights,


Bruce Whitmore

1994 C&C 37/40+ "Astralis"
Madeira Beach, FL  

(847) 404-5092 (mobile)
[email protected]



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