[C320-list] Engine/Shaft Noise and Vibration

[wflowe3 at aim.com]

 I have a similar situation with my 2008 boat. I've had the Marina check/align the shaft and I still have the noise. It starts at about 1900 RPMs and gets drowned out by about 2900 rpms. I too was wondering about balancing the prop but I have no idea how to do it.  It sounds like it is coming from the area of the prop while standing in the cockpit.

 


 

 

-----Original Message-----
From: Bruce Heyman <bruceheyman at cox.net>
To: C320-List <C320-List at Catalina320.com>
Sent: Sat, Feb 19, 2011 11:13 am
Subject: Re: [C320-list] Engine/Shaft Noise and Vibration


Dennis,
My bet is that if you aligned the propshaft you would be very happy with the  
result.  We used the process that is posted on our web site.  Took a while  
and the math is a bit conveluted but the result was delightful.
Bruce
Somerset 671 SoSal

Bruce Heyman
(949) 289-8400
BruceHeyman at cox.net

-----Original message-----
From: Dennis Harris <dharris02 at suddenlink.net>
To: C320-List at Catalina320.com
Sent: Sat, Feb 19, 2011 16:40:29 GMT+00:00
Subject: [C320-list] Engine/Shaft Noise and Vibration

Just curious if other C320 owners experience this.  I get a low level  
noise/vibration at certain speeds, and always have the fear that, despite  
what the mechanic said, the shaft may be striking the hull, but the  
frequency doesn't seem right.  The boat is a 2000 model (#694) with Yanmar  
3GM30F engine and transmission with 2.21 reduction.  The sound is a little  
like a very low level "whump, whump, whump".  The frequency increases with  
engine speed, but at higher speeds, the noise is largely overridden by  
engine noise and vibration does seem to increase significantly, so it may be  
noise more than vibration.  The cutless bearing is snug and there is no  
movement in the shaft.  However, in last year's haul out, on the forward  
edge of shaft strut, a small crack had come in hull fairing material.  The  
three remaining sides around the strut were solid and there was no leaking  
into the boat.  The four strut bolts were tight.  In previous haul outs,  
this area was fine, and the noise/vibration that I have mentioned has always  
been present through out the 10+ years that I've owned the boat.  There have  
been no issues (abnormal, frequent wear) at the packing gland. At ~2200 rpm,  
the intermittent sound occurs roughly 100 times/minute.  With the 2.21  
transmission reduction, this means that the sound occurs at a frequency of  
once per 10 shaft rotations, so in my mind, I have attributed the  
sound/vibration to be a harmonic of the combined system (hull, engine,  
shaft, etc.) and suspect that it's something not to worry about. But....what  
if?

Do others experience this?  Is it a problem that needs to be addressed, and  
if so, how?

Thanks,

Dennis Harris
C320 #694, Washington, NC