Major Drive Shaft Wobble Under Midrange rpm

[albergsailor]

i have a 2 cylinder volvo penta diesel model 2002 in my boat. To start with i have attributed the wobble to simply being a problem with the motor mounts. The motor is simply held in by gravity which i see is how many other (even yanmar) motors are held in. This blows my mind that a company could be so stupid to sell something like this. I already put custom motor mounts that go to the rubber mounts because the origional ones that come off the motor are very weak and break. also i just replaced the cutlass bearing/packing and realined the motor so that it is perfectly aligned with the rear shaft. I need to take another test run and see if anything should be adjusted but i seriously think that this is just simply a major design flaw and that more customizing needs to be done. I need to have mounts that actually hold the motor in place and dont allow the motor to wobble which will cure my driveshaft wobble. yea i believe i already have it figured out just thought i would share this and see if anyone else has had this problem.

[Eric M]

If the cutless bearing is new, and the shaft is straight, and the alignment is proper any vibration in the shaft has to be coming directly from the motor. We just replaced the mixing elbow on our yanmar due to a couldn't reach full rpm issue and a side benefit was a reduction in shaft wobble at midrange rpm. Is it possible you have either a partially plugged elbow or injector causing the engine to vibrate more than designed?

[Unicorn Dreams]

Prop bent? Doesn't take much, not always visible by eye.

Loose prop nut?

And the best of all, check your prop shaft zinc, had one on friends boat that one bolt and nut came off. Caused one hell of a wobble..

[albergsailor]

bad motor mounts, yep i have 3 custom motor mounts left to make, i already made 1, that was the problem the motor shakes all over the place on every mount, i have no idea how those origional mounts are supposed to work correctly at speed. ill put some pictures up when im all done, i double checked everything including the alignment of the motor to the shaft its obvious its the mounts