3.0l mercruiser i/o pontoon vibration

[Racefab72]

Trying to get opinions on what to check on my 1999 25’ suntracker I/O 3.0 with alpha 1 gen 2. I bought it a month ago and had the prop fixed prior to taking it out for the first time, previous owner is a good friend and said he didn’t ever notice a vibration. I can decrease the vibration by following the rpm with the trim, as in raising the trim a bump of the button to knock the vibration off. Any idea on where I should start checking vs. just tossing parts at it?

 

[alldodge]

had the prop fixed prior to taking it out for the first time

What damage did the prop have and the placed that fixed it, did they balance it?

If prop is not the issue
Take the prop off, attach a dial indicator to measure the run out of the prop shaft
Could also try another prop to see if it changes

 

[Racefab72]

Not sure about balancing, it had a couple 1/2” chunks missing so they added pieces to it and cleaned it up. It supposedly a reputable place in Troutman nc but I’ll call and verify if they balanced it tomorrow. Would ujoints typically cause this or would it be at any angle?

 

[Grub54891]

U-joints could cause it, just like a front wheel bearing in your car, when turning it gets noisier or changes pitch. A gimble bearing would make noise also, if bad enough it would vibrate.

 

[Racefab72]

U-joints could cause it, just like a front wheel bearing in your car, when turning it gets noisier or changes pitch. A gimble bearing would make noise also, if bad enough it would vibrate.

My wonder is will it get better if you trim it up slightly while riding? This does, and at lower rpms it’s practically not there

 

[Grub54891]

My wonder is will it get better if you trim it up slightly while riding? This does, and at lower rpms it’s practically not there

Anything is possible. If it's bad, no telling what it will do under different loads.

 

[alldodge]

Anything in the drive line (drive, prop shaft, U joints, drive shaft, coupler) can cause a vibration. Even a small vibration can due harm over time.

 

[Scott Danforth]

pull the drive and inspect the alignment, u-joints, bellows and the gimbal bearing. that is an annual service inspection.

 

[Racefab72]

pull the drive and inspect the alignment, u-joints, bellows and the gimbal bearing. that is an annual service inspection.

So being a new sterndrive owner is this typically an every year check that y’all do?

 

[Scott Danforth]

it is what is recommended in the manual. typically people leave it until something breaks and then pay 20 times what it would have cost if they simply followed the recommendation in the manual. that whole ounce of prevention vs a ton of cure thing.

pulling the drive and inspecting the alignment is done so you dont tear up the coupler. the greasing of the spline shaft keeps you from tearing up the coupler splines

inspecting the u-joints will normally catch issues well before a catastrophic failure

inspecting the gimbal bearing will normally catch issues well before a catastrophic failuer

inspecting the bellows will normally catch issues before they leak and take out the input shaft and seal from water entering the bellows and rusting the shaft which in turn causes your drive to leak oil into the bellows, thus grenading your drive due to low oil.

greasing your prop shaft also prevents your prop from becoming one with the shaft which means you have to cut your prop off.

every 3-5 years change the bellows and raw water pump impeller.