Vibration - I'm out of ideas. Please help

[petedw]

I have a 1979 Renken with a 140 mercruiser. I have a bad vibration that shakes the whole boat. The vibration is with and without the outdrive on the boat. So it doesn't seem related to alignment in any way. I also changed out the engine coupler because it seemed warped (I would align the motor and then turn it over and the alignment would be off). The motor seems to run fine and I have checked the compression on all cylinders. It is likely that this is more of a boat issue than a motor issue?

 

[Phfantasm]

Re: Vibration - I'm out of ideas. Please help

here is an idea... but will take some work...we know its not the outdrive, so it has to be engine,flywheel (flexplate) or coupler.... if your handy enough to change a coupler, you should be able to handle pulling the motor out. I would remove the coupler and flywheel, inspect the flywheel for loose bolts or for a warped flywheel... it is possible to have a concern there....
Also, make sure the motor mounts are still good and the motor is "isolated" or not "grounded out"... and component of an engine that contacts a frame/boat will transfer vibration (normal vibrations) bypassing the motor mounts ,which are designed to "isolate" this from the boat.... hope that makes sense