motor vibration

[Keven]

When I run my Yamaha 115 trimmed down I get this intermittant vibration between 3600 and 3900 rpm. If I trim it up, it goes away. I checked the lower unit oil and it was full and very clean. The prop and prop shaft seemes tight and spinning freely as well. I also pulled the cover and checked the fly wheel and listend while running. Still clueless. Any Ideas ??

 

[diver18]

Re: motor vibration

Any damage to the lower unit and is the prop OK?

 

[Keven]

Re: motor vibration

I pulled the boat out of the water , checked the oil level in the lower unit. It was perfect. I spun the prop to see if it was warped or bent, looked fine. I pulled the cowling and checked the the flywheel. I ran it like that for a short distance, still noticed nothing unusual. I called a local mechanic , he's taking it for a ride tomorrow. After explaining the situation, he thinks it could be the engine having a hard time transistioning from one jet to the other. Keep my fingers crossed. Thanks

 

[swist]

Re: motor vibration

Are you sure it's coming from the engine itself? Many boats have certain settings of RPM, trim, etc that will cause some sympathetic vibration in<br />various parts of the boat. Should never be severe, though.

 

[Keven]

Re: motor vibration

Swist,<br />I had the mechanic run it with me, he said it was the inner prop bushing being corroded or loose. SO the prop neds to be rebuilt...better than the lower unit