[C320-list] Motor mounts

[Greg Flanagan]

I just thought I would add my experience on shaft resonance. 

I had a local company align my shaft. The business tech/owner spent over an hour and I had to run the engine a number of times while he “tuned” it. When he was “finished” we had about three rpms that ran with no rattle or knocking. He said that was what it was on my Yanmar. I worked with these 3 speeds for years as one was a good cruising speed. 

     Then I met a fellow from my Austin Healey club whose was a trained and certified Yanmar mechanic. As a friend he came out to the boat to have a look. I asked if I needed to run the engine and he said no. He worked for about 10 minutes and said he was done. We ran the engine through its range and there was no shaft rattle or knock at any rpm. I now have a few years of use since then and it has always been smooth throughout the rpm range. The message in this story is that a competent mechanic should be able to align the shaft for smooth operation barring some other equipment failure.

Greg
Hoop Dancer #1076
Sidney, BC

> On Nov 5, 2023, at 7:00 AM, Bruce Heyman via C320-list <c320-list at lists.catalina320.com> wrote:
> 
> Hi Dave,
> My experience has always been that when you have specific rpm's that results in resonance it is either due to shaft whip or misalignment of the shaft. In the past when I've had that problem it would go away when I aligned the shaft. Also, my experience is that when a motor mount fails you have very serious shaft misalignment and when you look at the motor mount you will see the rubber is detached from the metal.
> Bruce
> Bruce Heyman
> Somerset #671 San Pedro (LA) California
> 
> -----Original Message-----
> From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of Dave Hupe via C320-list
> Sent: Sunday, November 5, 2023 6:48 AM
> To: C320-List at Catalina320.com
> Cc: Dave Hupe <hoopdtwo at yahoo.com>
> Subject: Re: [C320-list] Motor mounts
> 
> I have the Perkins M30 engine in my 1994 #32. I have vibration that I don't like at certain rpms and the engine does not like idling too low. I have examined my motor mounts and manually jiggled theengine as hard as I can, but don't see/detect anything that says I should replace my mounts. I have learned to throttle up/down to get a smooth motor cruise for different speeds desired and an easily get 6 knots without pushing the engine hard. I don't like the idle speed my motor wants when it comes to shifting between gears without the motor shuttering. Shifting sounds harder than i like but it works.
> NOTE everyone .... I suggest mention your specific engines when doing posts like this. Specifics helps each of us know the applicability of your information to our own situations.
> Dave Hupe
> 1994 C320 #32
> Holland, MI
>