[C320-list] Engine/Shaft Noise and Vibration

[Dennis Harris]

Bruce,

Thanks, I've downloaded the procedure.

Dennis Harris
C320
# 694 Washington, NC

----- Original Message ----- 
From: "Bruce Heyman" <bruceheyman at cox.net>
To: <C320-List at Catalina320.com>
Sent: Saturday, February 19, 2011 12:13 PM
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