[C320-list] Engine/Shaft Noise and Vibration

[Dennis Harris]

This is my understanding: It's done on dynamic machinery somewhat similar to 
dynamic balancing of tires for your car.  Before the prop is balanced, it 
should be checked with templates for that particular propeller to make sure 
the blades are not bent (bent blades will cause vibration problems).  If 
it's out of balance, they remove metal at the hub to compensate.  Barbour 
Boat Works in New Bern, NC (now out of business) had the capabilities years 
ago.  I had them re-pitch a propeller for my pervious boat. It was done by 
eye, hammers, and checking to make sure the angles and profiles were 
correct.  Definitely a skilled professional's job.  At the time, the shop 
was filled with perhaps 10 matched pairs of large motorboat props intended 
for Hatteras Yachts.  The technician told me that Hatteras had changed 
engines on a particular model and the props were being re-pitched to match 
the new engine/transmission set-up.  It was interesting to watch him work.

Problem is that I don't know who I should get to check the balance.  I'm 
open to any first hand knowledge here.

Dennis Harris  C320 #694 Washington, NC

----- Original Message ----- 
From: <wflowe3 at aim.com>
To: <C320-List at Catalina320.com>
Sent: Monday, February 21, 2011 9:55 AM
Subject: Re: [C320-list] Engine/Shaft Noise and Vibration



 How does one check/balance a propeller ?








-----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
>