[C320-list] Vibration under power issue

[Rick]

Michael,
You have  replaced several items common to a shaft replacement and a timely
maintenance schedule. Just wondering if you are using the OEM fixed prop and
did you have that prop trued and balanced?  I trust that the yard had the
shaft couplers matched/machined with the proper fit. Also, did you replace
the shaft log ( to hull tube) hose given the age of your hull at the time
you had the shaft replaced? 

The reasons I ask about the prop is because given that the vibration is
taking place approaching a cruising speed and after the yard checked the
alignment,  an unbalanced prop condition may be the likely source of your
vibration if the alignment was performed correctly and providing that the
shaft is true and the couplers were properly installed. If you have a
folding prop, then that also could be the source of a vibration.

 We had the unfortunate occasion of catching a line in the prop and that
resulted in a noticeable vibration due to bending the OEM brass shaft and
also deflecting the fixed prop blades. The shaft was replaced with stainless
and I was charged for having the prop trued and balanced. I still had a
vibration after the shaft replacement and I checked/improved the shaft
alignment with only a small improvement.  I pulled the OEM fixed prop and
had the prop trued and balanced a second time (this time for real),  and
then the vibration issue was resolved. While the prop was worked up to look
like new when it was installed by the yard, the prop was lacking a proper
balance/trued condition. I took the prop to an old timer who used his old
school methods and that did the trick!

I bring up the shaft log hose issue only because after I switched to a Buck
Algonquin hose that is more robust (stiffer) did I visually observe even
less shaft vibration while the engine was idling.

Hope this reply is helpful

Rick 
My-Ria
95 320 hull # 277.  

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
Of MSail
Sent: Wednesday, July 27, 2016 3:37 PM
To: c320-list at lists.catalina320.com
Subject: [C320-list] Vibration under power issue

I'd appreciate any feedback from the fleet regarding a vibration issue that
arises above about 2000 engine rpm.

1996 C320
Westerbeke 30B
JS Transmission
16" Max Prop (3-1/4" clearance tip to hull)

Problem:  In gear, vibration/rattle above 2000 rpm, increasing further as
engine speed increases to maximum.    Engine and transmission moving
considerably on mounts when vibration is encountered. In neutral, engine
runs smoothly to max rpm, no vibration.

I've replaced:

Engine mounts (with Westerbeke OEM original types) Prop shaft (from original
bronze to Aquamet 22) Cutlass bearing (replaced 2 years ago, showing some
wear as of 7/16 but not deemed excessive) Done careful shaft-transmission
coupler alignment with yard.

Have NOT replaced damper plate. 

Thanks in advance for comments.  Has anyone else on this list experienced
this problem with this setup?

Michael  Mellon
Santa Cruz, CA
msail at baymoon.com