WE have a 1998 Carver 500 with twin Cummins (6TAC8.3-M2) 350 Diamonds 450hp and it vibrates like you where standing on a orbital sander. It's so bad you would think the mirrors in the aft cabin are going to break. We have been chasing this problem for five years. Motors alignment confirmed three times, new shaft starboard side, two new cutless bearings, re mounted starboard strut, refiberglassed strut mount starboard side, props changed and computer speced all good. The bucket is almost empty spent 20+G Any ideas?
Inside the starboard engine. Possible bent rods, crankshaft etc. Judging by refiberglassing and replacing the starboard motor mount. Rev it up in neutral and see if it vibrates. Go on a seatrial and bring one engine up to 2300 rpms at time.....(or near full throttle), it probably won't achieve 2300 on one engine with the higher load factor.
Have you tried running it up in Neutral (crank, rods) although I'd have thought you'd have blown the motor by now? Motor mounts OK? If that doesn't bring on the shakes, try disconnecting the shaft, putting it in gear and running it up (transmission)? If still no shake, given what you've done so far, the only things left at the shaft coupleing, the shaft log or stuffing box. If you're dripless is it getting lubricated?
Thanks for the feed back I will preform the tests as you have suggested this weekend and post the findings Thanks again
Vibration Well after trusting marine mechanics to do a good job it was MY turn I started with the basics The actual motor mount to the stringers Twelve bolts in each Found some bolts finger tight On the whole 96 maybe six where tight That done I next tested the boat one engine at a time found Starboard moved 1/8" both front and back from idle to full throttle Port 1/4" back 1/8"front Much better Next disconnected coupling and checked output shaft side play with a dial indicator ~ .001" all good Turned the output shaft by hand to get a feel of the condition of the bearings all felt good at slow speed but once I turned it quickly I could fell the gear lash was a little rough I Believe the reason for this is the engine has been out of align for years and moving up to ¾” up on the stern due to the loose mounts My next plan is to add Flexible shaft couplings from R&D Marine Any thoughts
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