[C320-list] Vibrations at certain RPM Range

[kskis at aol.com]

As I responded recently, my "whining" or "singing" between 1800 and 2500 rpms in forward gear only, could be a prop issue.  I have read that some prop people are familiar with creating an "anti singing edge-a chamfering of the trailing edge, typically on the suction side..." (ref:HydroComp, Inc.).   If a prop issue, this could be determined by replacing the prop with a "working" 3-blade prop from another C320.  Wondering if anyone can direct me to a fixed 3-blade 9x15RH prop for sale?  Or any other suggestion?  Thanks.  Neil Kornblatt Harmony #973 


-----Original Message-----
From: John Meyers <jcmeyers7 at gmail.com>
To: C320-List <C320-List at catalina320.com>
Sent: Tue, Aug 6, 2019 10:38 am
Subject: [C320-list] Vibrations at certain RPM Range

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