[C320-list] Vibrations at certain RPM Range

[Scott Thompson]

We have started getting a racket periodically from the front engine cover vibrating. Sounds like someone shaking a can of rocks with an occasional squeak. It goes away if you stand in front of it, which makes diagnosis difficult. Probably the cover latches are not as tight as they were 20 years ago. 

> On Aug 7, 2019, at 3:15 PM, Chuck Mueller <katchu at chartermi.net> wrote:
> 
> John:  
> I've noticed that the lazerette covers and the center seat tend to vibrate
> at that RPM.  Cushions help a lot.  Also, my companionway ladder just
> touches the engine cover on the starboard side and it can set off a racket.
> I have not figured out a solution yet, but will probably put some spacers at
> the top of the ladder to push it out a little.
> Chuck Mueller
> Northwind 676 (2000)
> Holland, MI
> 
> Message: 4
> Date: Tue, 6 Aug 2019 10:38:16 -0400
> From: John Meyers <jcmeyers7 at gmail.com>
> To: C320-List at catalina320.com
> Subject: [C320-list] Vibrations at certain RPM Range
> Message-ID:
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> 
> Starting about 3 weeks ago the boat is making a loud racket when the engine
> is revving between 1500 and 2000 rpm. mostly in the rear of the boat but I
> cannot pinpoint the source. This occurs both in gear and in neutral so not
> suspecting shaft alignment. I suspect that it is some harmonic thing. All
> motor mounts look good and solid and well attached with over a quarter inch
> between the metal parts. I have check both feeling and/or removed just about
> every thing in the lockers like spare prop, spare anchor, propane tank, and
> other items that might be shaking while the noise is occurring. I have felt
> the fuel tank and engine and nothing feels different than when the noise is
> not noticeable. I have even gone below the boat and felt the shaft prop
> cutlass, rudder and all seem solid. The shaft and cutlass bearing were
> replaced a couple years ago. I have checked the steering mechanism.
> 
> To explain the noise/clatter it sounds like a loose hatch, door, or
> equipment is shaking.
> 
> At low revs and higher revs the noise is not there.
> 
> Has anyone ever had this problem or know someone that has/had this problem?
> 
> Thanks for all your help in past, present, and future. I rely on the
> questions and answers this list provides.
> 
> John Meyers
> Wind Chime 1997 #406
> Muskegon, MI
> 
>