Rebuilt 3.0L Mercruiser Inline 4, Vibration noise

[taylorsfields]

Hey everyone, thanks for the all the help, this is my second post.

I recently took everyones advice and replaced the crank, main and rod bearings, and gaskets on my 3.0 Mercruiser.

It runs near perfectly, accelerates fine and slows fine. It works flawlessly for the first couple minutes.

After it nears operating temp, a vibration type noise appears after 2000 RPM. It appears to be coming from the back of the motor, but sounds like valve rapping.

I recently swapped out the cylinder heads, all the bearings, the water pump, alternator, lifters, rods, fuel pump.

I currently have the outdrive off and it still makes the noise (though I do need a gimbal bearing also)

this is driving me crazy, i'm ready to sink it!!! hopefully someone can sort through this mess of a post and help me make sense of my waste of money!

Thanks,

Taylor

 

[Grub54891]

Re: Rebuilt 3.0L Mercruiser Inline 4, Vibration noise

Did ya locktite the flywheel/coupler? I've seen em come loose with bad results......
Grub

 

[alldodge]

Re: Rebuilt 3.0L Mercruiser Inline 4, Vibration noise

When you were installing the new crank and connecting rod bearings did you use plastic gauge? If so what readings did you get?

 

[taylorsfields]

Re: Rebuilt 3.0L Mercruiser Inline 4, Vibration noise

thanks for the suggestions guys,

I just pulled off the dust shield for the flywheel. The noise went away somewhat, but another noise was more audible. I went over and pulled upwards on the starter, and the noise lessened. There's a bolt on the back of the starter that looks like there might be a third anchor point?

I think the next plan is to loosen the starter bolts and then re tighten while pushing up on the starter...

Just weird it only does it warmed up.., maybe the flywheel isnt quite balanced and the motor hits the harmonic note at a certain temp/rpm?

I'll post results for anyone else having ghost noises.

Thanks everyone