[C320-list] Engine/Shaft Noise and Vibration

[Karl Mielenhausen _/)]

Dennis,

My Mainsheet article  
(http://www.catalina320.com/article.php/20090227141444654) might be of  
interest. I had several similar symptoms.
You may get lucky and discover loose jack bolts on one or more of the  
engine mounts, like I had.

Karl

On Sat, 19 Feb 2011 11:40:29 -0500, Dennis Harris  
<dharris02 at suddenlink.net> wrote:

> 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


-- 
Karl Mielenhausen
Catalina 320 Hull 690