Most Likely Cause of Water in Bellows?

After just pulling off my Alpha One drive unit, I'm surveying the damage that I think was caused by water getting into the U/J bellows. I've also removed the bell housing, shift cable and all the bellows.

Although the U/Js are still smooth, the whole assembly is rusted and the bellows were full of thick brown oil. So I'm thinking that water got in there somehow and has rusted the driveshaft seal track, letting the oil out.

Since I always store the drive down, and all the bellows seemed intact, could this have been caused by the shift shaft bushing leaking into the bellows? The bushing looks OK and the shift shaft is not worn at all in that area.

One other question. There is some corrosion on the U/J bellows flanges, both on the bell housing and the transom plate. On the bottom, maybe to within 3/16" towards the bellows groove. Can anything be done to fix that or would it still seal? I'm just wary of spending too much money and time if I can't fix everything properly.

Thanks.

Re: Most Likely Cause of Water in Bellows?

The shift shaft seal can leak, there is an overhaul kit for that, also there is MCM bellow sealant.

Re: Most Likely Cause of Water in Bellows?

the most likley cause if your drive is down is water filling up the hull and running into the bellows area from the engine compartment....change the u joints if theres no grease zerks on them....every one ive taken apart had some water in them....which spells disaster

Re: Most Likely Cause of Water in Bellows?

The most common reason for water in the bellows is a faulty (Old and cracked) bellows. On Mercruisers, rule of thumb is to replace every 5 or 6 years. After that, you are just pushing your luck.
While water can get into the bellows from the bilge, the water has to be over the starter to get there.
Another possibility is the big square cross section seal ring (Quad Ring) that goes between the drive and bellhousing. If it's in place, that is probably not your problem.
When you have water in your bellows, you have water in your gimbal bearing, ujoints, and probably the drive. The yoke that is in the drive may also rust and take out the front seal of the drive.
Did you check for water in the outdrive? The seal is not designed to prevent water entry, only to keep oil in.

Re: Most Likely Cause of Water in Bellows?

Thanks, bassboattech but I meant that I stored it with the drive down on the trailer, (to preserve the bellows). And the boat is double covered, so no rain ever gets in.

Yes, I realize the U/Js will have to be changed and probably the center and aft yoke and the seal. I'm resigned to that.

I'm more concerned about the U/J bellows flanges and whether they will seal properly after I've cleaned off the corrosion damage. It's a 1986 Doral with an Alpha One. If I had to get one, a new bell housing shell is $550 and the transom plate a lot more so it may be uneconomical.

Re: Most Likely Cause of Water in Bellows?

I'm more concerned about the U/J bellows flanges and whether they will seal properly after I've cleaned off the corrosion damage. It's a 1986 Doral with an Alpha One. If I had to get one, a new bell housing shell is $550 and the transom plate a lot more so it may be uneconomical.

Click to expand...

Ayuh,... Of course, We can't see just what you can,....
Depending on just What you're seeing,...
I'd think an Epoxy might help,...If it's just eroded abit...
If there's flange actually Missing,... Replacement would be the answer...

Re: Most Likely Cause of Water in Bellows?

Thanks, guys. I'm kicking myself for not pulling the drive sooner. It'll come off every fall, from now on! And yes, the gimbal bearing will need to be changed.

Don, the rubber quad ring was in place and the lower unit oil was clean although I had renewed it in the spring and it's always been clean before. I know that the aft yoke seal track will be rusty so will need renewing and a new seal, together with new U/Js.

If I do this, and the bearings are OK, can I re-use them as is, or do I have to use a new pre-load spacer? I see bearing assemblies are offered ready pre-loaded but am not sure. I can measure the gear engagement before I take it out and maybe shim it back to the same dimension.

With the U/J bellows flanges, they still have the grooves all around and the face under where the clamps go is solid. I might sandblast the corrosion off and smooth out the pits with JB Weld. It's just at the bottom on the U/J bellows flanges only.

Re: Most Likely Cause of Water in Bellows?

Make sure that your shift shaft seal is of newer type, not the tiny original one. I had water in my drive bellows because of that seal.

Re: Most Likely Cause of Water in Bellows?

frank246 and Aviator5, I think you got it. Thanks.

I pulled the upper shift shaft last night and removed the seal. The shaft has cleaned up just like new, no marks and still shiny. The bush looks OK but the brittle seal just fell apart when I removed it. It is the tiny one.

Also, there was no white plastic washer under the top lever, so someone has had this off before and left the washer out. I'll look for the updated seal.

This is a low time trailered boat that I bought used and the outdrive appears to be in remarkably clean condition from the outside. The PO stored the boat in his garage. Just shows you can't tell much from that.

The main part of the shaft is in the exhaust cavity which would be full of water whenever the boat is moored. So water can seep up into the U/J bellows if the seal is weak and has no way out except back through the seal. That does look like a weak point on an otherwise fine design.

Re: Most Likely Cause of Water in Bellows?

Mercruiser has a kit to replace that tiny seal, it contains a new bushing with 2 heavier seals in it.