Bellows adhesive or not?

[tfret]

Im installing new U joint and exhaust bellows on an 07 SX-A drive. Neither the instructions that came with the OE kit, or the service manual call for adhesive. However my sealing surfaces were a bit corroded. After cleaning them up they are a little bit pitted. I’m considering using adhesive just to ensure a good seal. What harm if any could possibly be from this?

 

[Scott Danforth]

I would wire brush the corrosion, use a zinc dichromate primer, and some paint prior.

 

[tfret]

Yep i got it all cleaned up, primed, and painted with Volvo primer and paint. But still not perfectly smooth like it was when new.

 

[Horigan]

I use Triple Guard grease.

 

[4now04]

I would not recommend adhesive. The drive bellows is secured with a hose clamp on one end and compressed between metal drive parts on the other (or at least it is on my DP-SM). The exhaust bellows does not need to be water tight. In fact, the bellows has drain holes in it.

 

[BRICH1260]

Having a watertight seal on the exhaust bellow is not critical. As long as you have enough lip to get the clamp to tighten on you should be good. Adhesive isn't detrimental until you go to replace that bellows with the next one, it can really gum up the mounting surfaces for the next time.

 

[HiWard]

From my VP Workshop Manual AC 2(2) from 2003, on page 43:
"Coat the outside surface of the gimbal bearing bore with Volvo
Penta Gasket Sealing Compound. Sealer is not required on the
outside of the exhaust opening."

and page 61:
"Apply Volvo Penta Gasket Sealing Compound around the complete inner V-shaped lip of the pivot housing, to seal the
U-joint bellows against water entry."

Someone else may be able to confirm this, but my understanding is that VP at some point changed the bellows from a rubber type to a harder plastic type. Maybe the latter doesn't require gasket sealant?

 

[Grub54891]

I never put adhesive on the exhaust bellow. I used to but it would pull off the transom end sometimes. Then I read that it's not needed. Volvo not so bad but does happen at times. Mercruiser seems to come off almost every time with adhesive.

 

[tfret]

Hi and I appreciate the dialogue very much. Yes of course I realize the exhaust bellows isn’t critical for being water tight. The exhaust is full of water anyway. Protecting the U joints on an older drive is my priority. Weighing the difference between making the bellows replacement more difficult next time VS having a leak that ruins my U joints (non greasable), Im leaning toward sealant. I guess my question really is, what harm could possibly come from this?

 

[Scott Danforth]

if you want to use a sealant, use permatex #3 non-hardening. it can be cleaned off with mineral spirits

 

[Lou C]

When I do the Cobra bellows I've followed the OMC shop manual and used their gasket sealer on that flange, what I have found is just like with threaded fasteners, it keeps out moisture and the last time I changed the bellows (old one was in use in salt water for 11 years) the flange looked perfect. No corrosion at all. Permatex Aviation is a good alternative, it seems that both the original Merc Perfect Seal and the OMC/Evinrude gasket sealer is very hard if not impossible to find, or places that appear to be selling it, actually send you a can of the Permatex!

 

[IslandExplorer]

If you're worried about it leaking bc of somewhat conpromised surface and don't mind spending a few minutes years from now cleaning off a little sealant- then seal it up good! You'll probably feel better about it later when you're out there. I like the kind that sets vs slippery/greasy type. Think I used Quicksilver brand. I would put some on there if it were me. Won't hurt a thing. No one wants u joints that you can't see rusting.

 

[tfret]

Thank you all for the inputs!

 

[Kosmofreeze]

A timely thread since I'm finally going to change my VP DP-SM bellows that was last changed in 2011. While the rubber still looks and feels good after 14 years and 160 hours of fresh water (dry stored) it's probably time to change it. I've never done it before. The local VP shop wants over $2K to do the bellows and gimbal bearing - that's my incentive for DIY. For that kind of $$ I'm sure they'll recommend to change the rubber every year. What's a practical maintenance interval for replacing the bellows given that the boat is lightly used, fresh water and dry stored? Every 5 years?

 

[Lou C]

I look at a driveshaft bellows like I look at tires, if I see small cracks starting to form it is time to replace, that is a sign that the rubber is becoming less flexible. Tilt the drive all the way up and look in between the folds, if you compare an old bellows with a new one you can see and feel how much stiffer the rubber gets over time. Also turn it side to side, see if you see any signs of abrasion as well. In my use (salt water, moored boat 6 months, but when stored drive is down) I start to see cracks after about 10 years of use.
If the gimble turns smoothly when turned with fingers, and you're not getting any noises from the drivetrain I see no need to replace it. Mine was last replaced about 20 years ago, never any water in the bellows since then, it gets greased at the beginning of each season with the engine running and that's it.

 

[KM7]

Is there a way to tell if the U-Joint Bellows is leaking? That would be very good to know because a leaking bellows can lead to having to replace the U-Joints and the Gymbal bearing and possible worse.

There is a plug on the starboard side to check if water is getting into the cavity where the shift lever and the shift cable guide move back and forth.

Is there a way to check for a leak at the bellows? It seals on the forward edge with a hose clamp and at the aft edge just by pressing against the bearing carrier on the OD. To me, that seems like it would not be that reliable.

I'd sure like to be able to check that I got a good seal.

Any suggestions?

 

[IslandExplorer]

I'm no outdrive expert but I am not aware of an inspection port or drain for the drive bellows on a Mercruiser. Basically if the water gets in there, the damage is already done is the way I look at it. The u joint is just basic automotive stuff and will rust up immediately if run in any salt water. You might get away with water in drive bellows a couple start ups if it was fresh only but I'd think your joints would be seizing up nearly same day as salt water intrusion. Gimbal shortly after. If you had a really serious leak it would come in through the transom plate as the shaft is not sealed there and bilge would be running to compensate.

 

[Lou C]

There really isn’t any way to know if the bellows is leaking as long as the drive is installed although if it does leak eventually the gimble bearing will get noisy. This to me is one of the essential drawbacks of I/O power packages and why among other reasons I won’t have another. In fact at one point I think Volvo had incorporated a moisture sensor into the bellows which is a great idea if it actually worked. This is also why all I/O manufacturers recommend removing sthe drive at the end of each season; if there’s been a problem developing you will find it then. But what do people do? They do deferred or non existing maintenance and that’s part of what gives I/Os a bad rep esp in salt water regions; an old mechanic I knew refers to them as “double trouble” lol. If maintained they can be fine even in the brine but it you want low maintenance they’re not it; outboards are!
If the Cobra bellows is installed properly it should not leak and mine have easily lasted 10 years.

 

[KM7]

Thanks guys. While a leak into the bellows will cause rust on both the U-Joints and the Gimbal Bearing, I don't think either one would seize or become noisy immediately. I experienced a leaky U-Joint bellows when the clip that connected to the ground wire and the zink pieces got out of position and cut the bellows. It may have been like that for months, based on how the drive shaft looked. The U-joints were still fairly smooth, and I considered not replacing them but decided that I would. The gimbal bearing did become noisy, and I replaced it. It was difficult to get it out due to the rust. I also had not been lubricating it as frequently as I should have.

One possible way to check for water in the bellows would be to loosen the hose clamp on the forward end and see if any water comes out. You can do that without removing the OD completely.

Water in the lower unit gear oil would indicate a leak possibly into the U-Joint bellows and then past the seal in the bearing carrier into the gears.

 

[Lou C]

Here’s why I wouldn’t do that. For one due to the folds there could be water that wouldn’t drain out but enough to rust the gimble & ujoints. So you might not see a leak but there could be water in there. For another you know how the front edge of the Cobra bellows seals, with the ridge in the bellows sealing surface having to fit into the groove in the gimble housing. It might not reseat correctly thereby causing a leak. If you pull the drive at the end of each season & carefully inspect the bellows I think you can avoid problems. As soon as you see cracks starting in the folds replace the bellows.
Of course if you REALLY want to be fussy after your first few runs pull the drive and check it after a bellows change, it only costs you a gasket. I have a drive jack so the R&R is very easy…..