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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10641
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 454 mercruiser 300hp inboard (year 2000) v-drive

Customer Question

I have a 454 mercruiser 300hp inboard (year 2000) v-drive transmission
We have had a slight vibration all summer but the last time we took it out it idles fine and in neutural revs up fine, but in gear it idles fine but reving up vibration starts and gets really bad at 1000 rpms and engine starts vibrating badly and making a loud noise. I cannot increase rpms because of vibration and noise. We thought it was a prop problem but that checked out. The transmission fluid is good and the noise is on the engine and
and not on the transmission.
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

The problem is most likely engine alignment. You need to check the engine alignment at the prop shaft coupler at the rear of the transmission. The other possibility is the cutlass bearing in the strut. Have you checked the bearing in the strut? You should have no shaft movement up and down or side to side. These are the things that will cause engine vibration. If these check good then you have an engine related issue. Which could be an ignition issue causing an engine misfire. The reason I think you have an alignment issue is the engine vibrates under load and you have noise.

These are the things I would check. This is something a person with experience needs to check and adjust. You should have no more than .003 clearance at the coupler.

Engine alignment should be checked yearly and every time the boat is pulled out of the water. Here is the alignment specifications.

Post back with questions and findings.

Expert:  Tan replied 1 year ago.

Please don't forget to positively rate me as that is the only way I get paid for helping you..

Thank you.........Tan

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