[C320-list] Vibrations at certain RPM Range

[Chuck Mueller]

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
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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