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1997 200 HP Johnson Ocean Runner Engine vibrates above 2900 RPMs

C

captain_mr

New member
"While riding our boat yesterd

"While riding our boat yesterday off Cape May, NJ my boat partner was operating the craft at 4500 RPM (24 mph) when the engine began to vibrate. The engine is mounted on an engine bracked but the bracket was not vibrating and appeared solid. He throttled completely down and the vibration stopped. When he throttled back up again there was no vibration until the RPMs reached 3000 then the vibrations could be felt. Any ideas what could cause the engine to vibrate at 3000 rpms? What should we look for?

Any help would be much appreciated."
 
"Hit anything? Slightly bent p

"Hit anything? Slightly bent propshaft, prop picked up something to throw blade off balance, something of that nature?"
 
"Joe:

Thanks for the reply.

"Joe:

Thanks for the reply. We did not hit anything that I am aware of when the motor started vibrating. Plus, why would the engine vibrate only after it got up to 3,000 rpms? If the propshaft is bent wouldn't it vibrate at the lower rpms? The prop is not obviously bent or misshaped to view."
 
"It would viberate of course B

"It would viberate of course BUT it happens sometimes that it is not noticeable until the engine hits a certain rpm.

Check the compression and spark to eliminate those areas. If the flywheel has magnets that are epoxied on, check to see that they are where they belong.

Is there any water within the gearcase, or heavy traces (slivers/chips) of metal."
 
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