Vibration at 3000+ RPMs

[Gymi]

I have a 2004 24V with a 6.0 Marine Power. I have a vibration at higher RPMs. I have had the prop refurbished. I have done a power test on all cylinders with my diagnostic software, and it's not a plug, wire, or coil. The vibration only comes at a load, in gear. And the engine/trans/vdrive doesn't seem to vibrate (I pulled the back seat off to observe vibration when driving).

Also, the output shaft is VERY close to the hole where the shaft comes out by the shaft seal. So I pulled the strut off to see if that was bent. With the strut removed, the shaft still stays far to the port side of the boat.

What might be the cause of:
a) the vibration
b) the shaft being off alignment

And are these two items related?

My thought is to loosen all mounts and shift the whole drivetrain, but before I do this, does anyone have the answer?

[dogbert]

Sounds like a bent shaft and strut.

[chpthril]

Was the prop refurbed due to a strike? If so, bent shaft or drivetrain knocked out of alignment.

[jciscott]

I have a long thread on vibrations... ending with me replacing my strut.... the WORST JOB IN HISTORY OF BOATING......
My strut was bent a good inch out of line... but the shaft was dead straight. There is a gouge in the old strut, like the previous owner put the strut on a rock......

[anhaney]

I have a long thread on vibrations... ending with me replacing my strut.... the WORST JOB IN HISTORY OF BOATING......
My strut was bent a good inch out of line... but the shaft was dead straight. There is a gouge in the old strut, like the previous owner put the strut on a rock......

Just dealt with that on my boat last week. Same thing. Better check the bolts on the shaft to trans coupler. If they are tight and OK. I would questions the person that repaired your prop. There is very few people out there who know how to repair ACME props and get them back to a no vibration position. If the prop is not the issue and you smacked it good check your engine alignment and strut. The center of the prop shaft should almost be center the to rudder. Mine is like 1/4 or less of center with the rudder in the straight position. If you want to talk on the phone about it give me a call 661-310-7666. I will walk you through the whole thing. It sucks dealing with it but it needs to be dealt with or you could be buying a VDrive next.