[C320-list] Engine/Shaft Noise and Vibration

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-----Original Message-----
From: Dennis Harris <dharris02 at suddenlink.net>
To: C320-List <C320-List at Catalina320.com>
Sent: Sun, Feb 20, 2011 7:46 pm
Subject: Re: [C320-list] Engine/Shaft Noise and Vibration


Karl,

I didn't find the Mainsheet article, but I did find a brief write up 
(perhaps a forum message that would appear to be from you on the same 
subject.  I downloaded it and will check out my situation.  Thanks

Dennis Harris
C320 #694

----- Original Message ----- 
From: "Karl Mielenhausen _/)" <C320 at suddenlink.net>
To: <C320-List at catalina320.com>
Sent: Sunday, February 20, 2011 1:20 AM
Subject: Re: [C320-list] Engine/Shaft Noise and Vibration


> 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
>