[C320-list] Severe vibration at 1000 RPMs after engine mount replacement

[Bruce Heyman]

Hi Paul,

If the vibration is the same regardless of the transmission setting then the problem is not with the shaft alignment.   

We have the Yanmar in Somerset so it could be different than your situation but our engine was extremely rough at idle and could take more than ten seconds of cranking before it would cough to life.  

I actually followed the manual for maintenance; adjusted the valve clearance (was quite surprised how much I adjusted them), sent the injectors out to be rebuilt, replaced ALL of the crushed washers in the fuel system, chased all of the rust and repainted, flushed the coolant system and cleaned out the heat exchanger, replaced all of the hoses, and cleaned and lubricated all of the cables.  Unlike a typical Bruce project it all actually worked.   I was amazed at how smooth the engine ran at idle (about 550-600 RPM) and how quickly the engine started.    I hate to admit it but there are some months that go by and I don't get to take the boat out.  During those times it was especially hard to start the engine and I sometimes had to bleed the fuel system.  Not now.  Can go several months and the engine still jumps to life.

I'm glad I chased all of the rust and repainted but my guess is the crushed washers, injectors and the valves were what made the difference.

Bruce
Somerset, San Pedro CA, #671

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Paul Borghese
Sent: Friday, December 11, 2020 8:17 AM
To: C320-List at catalina320.com
Subject: [C320-list] Severe vibration at 1000 RPMs after engine mount replacement

A boatyard replaced the engine mounts in my Cat 320 Perkins M30 engine. The engine is noticeably smoother at all RPMs except one, 1000 RPMs.  At exactly 1000 RPMs the harmonic vibration causes the engine to shake violently.

The vibration occurs every time on every transmission setting ( neutral, forward, reverse).

Any ideas as to the issue?  I have an uneducated theory. The yard used off-brand engine mounts that were not tuned to the engine causing the severe vibration.  Or maybe the bolts are not torqued to the correct specification.

Thoughts?


Paul