Alpha One Gen Two outdrive vibration

[Lou Bischoff]

I have a 2000 Sylvan 4.3 liter Alpha One Gen Two Mercruiser with an intermittent outdrive vibration. The events leading up to the vibration are:
1. Block was replaced 3 years ago. Runs perfectly
2. Upper half of outdrive leg was replaced last spring with a new SEI section due to seal leaks in original outdrive. Ran fine for full season. Outdrive alignment is perfect.
3. At end of full season, slight vibration at 1200 RPM's. Bigger vibration at 1800 RPM's. Knocking sound when turning hard left or hard right at 1800 RPM's. Gimbal bearing is original. Any thoughts on what is causing the vibration and knocking ?

 

[bman440440]

1st thing that pops in my mind is U-Joints esp since knocking when turning hard left or right... but you will want to replace the gimbal bearing too its over due.

 

[Lou C]

When you replaced the upper did it come with new u joints?

 

[Scott06]

Would pull the drive inspect gimbal bearing and u joints, issue there is most likely. I assume new Drive shaft and u joints came with upper drive, but id there was water intrusion could be an issue.look at gear lube for metal pieces, shavings are normal, but chunks not so. If those are ok might look into drive pop the cap on the upper.

did upper disintgrate when the seal leaked? If it was damaged metal could migrate into lower and smoke it.

 

[QBhoy]

Sounds like UJs

 

[Lou Bischoff]

Would pull the drive inspect gimbal bearing and u joints, issue there is most likely. I assume new Drive shaft and u joints came with upper drive, but id there was water intrusion could be an issue.look at gear lube for metal pieces, shavings are normal, but chunks not so. If those are ok might look into drive pop the cap on the upper.

did upper disintgrate when the seal leaked? If it was damaged metal could migrate into lower and smoke it.

Thank you, guys. I appreciate the feedback. The u-joints were new with the upper half SEI outdrive replacement. I followed the break-in procedure. The oil leak was a slow drip out the vent near the speedo hook-up. I caught it during winter storage in my garage last year. Pressure testing the outdrive pointed to upper half seal leakage, so I replaced the upper one. I don't think I had water intrusion or disintegration. The drained gear oil looks perfect. There is a very small amount of metal flakes on the magnetic screw from break-in. I popped the cap on the upper half, and the gears look new......no wear. Looks like I'm headed for a gimbal bearing replacement, and maybe a new upper half under SEI warranty. Any other thoughts ?

 

[Lou Bischoff]

Thank you, guys. I appreciate the feedback. The u-joints were new with the upper half SEI outdrive replacement. I followed the break-in procedure. The oil leak was a slow drip out the vent near the speedo hook-up. I caught it during winter storage in my garage last year. Pressure testing the outdrive pointed to upper half seal leakage, so I replaced the upper one. I don't think I had water intrusion or disintegration. The drained gear oil looks perfect. There is a very small amount of metal flakes on the magnetic screw from break-in. I popped the cap on the upper half, and the gears look new......no wear. Looks like I'm headed for a gimbal bearing replacement, and maybe a new upper half under SEI warranty. Any other thoughts ?

After I pull the outdrive, what are signs of the u-joints needing replacment ?

 

[Scott06]

After I pull the outdrive, what are signs of the u-joints needing replacment ?

roughness or binding. Kind of tough to explain something you need to get a feel for. I would also look for marks where the u-joints gimbal etc may have been rubbing on driveshaft/yokes - which is likely the knocking you hear.

Also look for water intrusion in driveshaft bellows.

 

[Rick Stephens]

Failing u-joints can present as fine when testing by hand manipulation. Unfortunately the only way to really know is to pull them apart and inspect the bearing surfaces, and if you do that it is easier to just replace them.

 

[Lou C]

if they are grease-able when you grease them does clean grease come out or is it watery and rusty? Certainly the latter would suggest they need to be replaced. I still have the original ones on my 34 year old OMC Cobra believe it or not. They should not feel excessively stiff or excessively loose. Turn the gimble bearing by hand and it should feel 100% smooth. Any roughness it needs to come out. And if its grease-able the same rule above applies, grease must come out clean and not emulsified with water.