Heavy Vibration

i4110peter · #1 10-09-2016, 07:34 PM

Went out Thurs, got boat up to speed, and I think something let go in the outdrive. Still goes into gear but vibrates so badly it's scary! I just had the gimble bearing replaced in March of 2015 and don't have many hrs on it since then. When engine is running in neutral, very noisy in outdrive but no vibration.
Any ideas? This is the mercruiser outdrive with the 165 hp straight 6. Thanks for any input.

steplift20 · #2 10-09-2016, 10:19 PM

Check the lower unit oil, I don't know to much about io but does it vibrate without it being in gear? I mean is the vibration coming from the engine?

garbubba · #3 10-09-2016, 10:29 PM

Used to have a few of those inline I/O's. That doesn't sound good, but it may not be a disaster.

Since you only feel the vibration in gear, check for endplay and loosness on the prop shaft. If that all feels good, maybe the vibration is just sympathetic.

Since it's noisy all the time let's assume for now it's in the upper half, the first place I'd suspect is the gimbal, if that joint starts to come apart it does just what you describe. That requires pulling the drive though so it may not be the smart place to start.

You could eliminate the upper gearset just by opening up the cover & see if things look OK there before you pull the drive.

The second suspect place is the bearing between the gimbal & upper gearset.

A length of hose or a stethoscope can usually narrow down where a noise originates.

Checking the gear oil should show if gears are chewed up.

spareparts · #4 10-10-2016, 06:21 AM

you can usually put your ear to the transom while its running and hear the gimbal bearing growl if its bad, turn the drive side to side, the u-joints will make some noise at full turn, thats normal, but if the growling gets worse, you know it the gimbal bearing. Check the gear lube and see if you have any metal in it. Upper gear issues won't cause it to vibrate, it will whine till the gears are gone. If it vibrates in nuetral, its either the engine,coupler, or drive shaft assembly. Pull the drive(put shifter in forward, remove the 6 nuts holding the drive in place, disconect the trim cylinders and it should coem off) and tell us what you find.. Also, look behind the engine at the cou[ler area, see if there is any aluminum dust or small black burnt rubber balls everywhere. BTW, propshaft end play is normal. Check your prop for damage. Check the propshaft by clmaping a coat hanger to the antiventalation plate wioth a pair of vise grips, bend teh end of teh cloaths hanger so its very near the center of the propshaft to use as a reference, spin the prop by hand and see if the center drill on the shaft wobbles. Don't pay attention to the shaft threads or the prop hub, they normally wobble, the only thing thats abo****ly true on teh shaft is the center point

macojoe · #5 10-10-2016, 10:14 AM

When mine was the same as yours it was Bad u joints

steplift20 · #6 10-10-2016, 08:40 PM

When you say the engine is running it's very noisy is that in gear or in neutral ?

steplift20 · #7 10-10-2016, 08:43 PM

Ok I just looked at your post again, you said in neutral so in neutral notting is turning am I right? And if it's noisy than it must be the engine? Do we agree Let us know so we can narrow this problem down , motor mounts could be the issue

garbubba · #8 10-11-2016, 03:01 PM

No. In neutral everything is turning except the prop shaft. That round part of the foot is where the forward & reverse gears are. But the water pump and the vertical shaft always run when the engine is running.

i4110peter · #9 10-11-2016, 06:24 PM

Took the boat up to a repair shop, hooked up water to the drive, stared the engine. No noise! Put outdrive in gear, no vibration. Going to take it to the lake tomorrow and test it in the water. Checked all that was mentioned above and no obvious issues.????

i4110peter · #10 10-12-2016, 03:51 PM

Took the boat down to the lake and got it off the trailer, started the engine, put it in gear and just about shook the back off. The only thing different is that I am putting pressure on the outdrive when in the water. the other thing I noticed is that when I use to spin the prop in neutral, I would hear a tick, tick, tick, and there would be slight resistance. Now the prop spins freely and no tick. I think something broke in the lower end. Opinions appreciated.