vibration

[Jim "SV Ohana"]

What is accectable vibration on these 25xp engines?? You can feel it in the whole boat. My only baseline is a yanmar 2cyl in a Watkins which vibrated quite a bit.
My engine seams to vibrate quite a bit in the 1500 to 2500 range, above that it smooths out.
The vibration seams to occilate.
Secondly, In attempting to lineup the shaft, I've found a 1 inch thick fibre spacer between the flanges, is this a damper??
Thanks
Jim

[Mike and Theresa Vaccaro]

Jim,

Lots written on this subject, will turn up with a SEARCH or FIND for shaft alignment, vibration, flexible coupling, or engine mounts.  Vibration is inherent in disel engines at low RPM--they smooth out as they accellerate.  If your vibration at higher RPM is not the result of a problem with your engine itself, it may be the result of shaft misalignment.  The "fiber spacer" between your shaft and coupling is probably some type of "shaft saver."  These are used to damp vibration (somewhat--but still require accurate alignment) but are primarliy designed to move the shaft slightly to mitigate wear from the shaft seal nut and cutless bearing.

The most inexpensive way to start trouble shooting is to re-align your engine (needs to be done in the water with the boat at a representative operating weight).  Also, recommend you check the condition of the engine mounts.  The mounts provided by Universal/Catalina are fairly stiff and transmit quite a bit of vibration to the hull.  The rubber in the mounts can be degraded if oil soaked (starboard forward mount is the most likely culprit since it lies under the engine-mounted oil filter) or otherwise mistreated.  These mounts can be replaced by "softer" mounts that de-couple the engine harmonics from the hull, thus reducing vibration.  Properly maintained (read "not abused") engine mounts should last the life of the engine.

Another option is to install a flexible coupling.  These couplings are fairly expensive, but go a long way to minimizing vibration caused by the rotating propeller shaft.  A good example is a Vetus Bullflex.  Although designed to accept some "misalignment," this type of coupling works best with the engine properly aligned.

Best of luck!

Mike