[C320-list] Vibration under power issue

[MSail]

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