[C320-list] Engine/Shaft Noise and Vibration

[Dennis Harris]

Irv,

Thanks for the suggestion. Any recommendations on who I should get to do 
this (ideally some one in/accessible to NC)? If the shaft/engine 
alignment/mount checks don't solve the problem, I get the prop balance 
checked at next haul out.

Dennis Harris, C320 #694 Washington, NC

----- Original Message ----- 
From: "Irving Grunes" <igrunes at gmail.com>
To: <C320-List at catalina320.com>
Sent: Saturday, February 19, 2011 11:50 AM
Subject: Re: [C320-list] Engine/Shaft Noise and Vibration


> Has your prop been balanced?
> Irv #851
>
> On Sat, Feb 19, 2011 at 9:40 AM, 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
>>