Gimbal Bearing Science

[Rivergator]

The gimbal bearing in my Alpha One Gen1 housing right now happens to be the sealed (non-greasable) type. The bearing itself feels good, solid and tight but it feels that it is lacking grease. You can tell by turning it by hand that it just doesn't have that draggy feeling of a well greased bearing. Since there is nothing I can do about it and I know that by next summer this bearing could go belly up on me I already ordered a new bearing and seal to have it ready when and should it happen and this time I made sure that I got the greasable type, the one that has the grease hole in it and needs to be lined up with the housing so it can be greased from the outside through the nipple. Today I got this bug up my butt and decided to look into it a little deeper to see how this all works and also to make sure that the bearing is properly packed by installing a grease nipple on the hole in the outer aluminum ring and pump some grease into it to see if it actually comes out somewhere. In my opinion some should definitely come out somewhere between the upper and lower race of the actual bearing that sits in the aluminum ring, but nothing came out anywhere. The pressure I exerted on my grease gun was quite severe and grease should have escaped somewhere for sure but the only place where some grease came out was where the nipple was screwed into the outer ring. Also I remembered a neat little demo Chris did where he put a gimbal bearing in a vice and then moved the bearing around in the outer alumunum ring. I tried that and no way did that work for me and I pushed hard to the point were the whole vice wanted to move but not the bearing, no way. That gimbal bearing is not swiveling. Coming back to the grease part. Has anybody ever taken one of these apart and actually has seen a grease hole going through the outer race of the actual bearing so that grease actually gets to the balls or is this all a scam and no grease ever gets to the bearing even though the bearing is sold as "greasable" just because it has a grease hole in the outer ring. Let's face it once the bearing is installed nobody knows what goes on with the bearing until if fails. We assume that we always lub'd the bearing when putting a grease gun on the housing nipple, but did we really. Suspicious minds need answers. At least the brand new bearing that I have on my bench acts like no grease is going into the actual bearing. On picture #1 A is the outside alu ring with the grease whole and B is the actual bearing. Picture #2 shows my temporary grease nipple. Picture #3 shows the actual bearing which I assume should be able to move inside the alu ring and can anybody tell me what the purpose for the 2 cut outs C is? Thanks

 

[Scott06]

Of it doesn’t swivel sounds like you got a pos aftermarket bearing definitely needs to swivel send it back

Looks like the grease hole in outer housing doesn’t line up with grease hole in race of bearing

 

[flashback]

Those cutouts are how the bearing is inserted into the carrier.

 

[Baylinerchuck]

The bearing will move in the aluminum cartridge, (carrier). It may be tight since it’s new. If you rotate the bearing so the bore of the bearing faces the aluminum of the carrier, the bearing will slide out through the slots in the aluminum. They sometimes need a little persuading by putting a prybar handle through the bore to get them to turn in the carrier. Once out you can locate the lube hole in the bearing race and make sure it’s toward the grease hole in the carrier when you reassemble. I’ve had one in the pastbthat wasn’t oriented properly and didn’t want to take on grease.

 

[tpenfield]

The problem that I have found is that there is typically not enough grease added to the bearings during the manufacturing process, so the bearing has a shorter life than it possibly could.

A new gimbal bearing will be difficult to move in the gimbal, and it usually takes the leverage of the alignment tool to get it to move. So, a bench vice would not be enough.

Another factor is if the transom assembly has the grease fitting and passageway to grease the gimbal once installed. I do not recall that my newer (2016) Bravo outdrives have the grease fitting, although my 1991 and 1996 outdrives had them.

I also suspect that the seals on a new bearing may be quite stiff and difficult to get grease to push them out. Much easier on a u-joint than a gimbal, is what I've found. I do recall on my older outdrives that grease would eventually come out of the seals around the bearing, but it took a while (it has been many years though . . . so not 100% sure) .

Last year, before the seasonal launching of my boat, I removed the outdrives to grease the u-joints, knowing that the gimbal was not grease-able . . . no grease fittings on the -u-joints either

Upon replacement (whenever that is) I plan on getting the grease-able type of gimbal gearing and at least load it up with grease as best I can.

 

[Rivergator]

Thanks you Gentlemen, it's been a long time since I got so much good information in such a short time from so many. Everything is pretty clear now in my head and I think I am gonna send the bearing back for 2 reasons. #1, it doesn't swivel, it is really tight. I cannot imagine it is supposed to be that way. I did use my alignment tool trying to swivel it, but it seems to be solidly stuck in the carrier ring, especially since I assume some of the grease I pumped in there should have spread around between the upper bearing race and the aluminum carrier and loosened it up some and #2 I won't be able to line up the grease hole in the upper bearing race with the grease hole in the carrier ring because of #1. Thank you all for sharing your great knowledge

 

[flashback]

I took an old one apart notice the small hole in the outer race, it must line up with the offset channel in the carrier.

 

[Rivergator]

Very interesting. And thanks a lot, flashback, for your effort to so clearly show how this thing is designed. Now this whole thing starts to make sense. I see now that it is not necessary that the hole in the outer race lines up with the hole in the carrier because of the offset groove in the carrier. Grease will travel down the groove and find the hole in the bearing and the bearing gets lub'd - bingo. I also know now that there is something wrong with my bearing. Even though it is brand new, it just doesn't want to swivel. And Good Golly Miss Molly, I tried. Maybe it isn't designed to swivel. Scott06 is right. It is a cheap aftermarket product that I bought and who knows where they cut corners. I already contacted the seller to look into it. The neat Youtube clip that Chris put up shows that it takes little effort on his part to move that bearing inside the carrier. Thanks for all the great info. I love to dig into things.

 

[flashback]

Glad to help, I've always loved tearing things apart too. After seeing how the bearing is designed I've decided to grease it while it's running. There are 2 holes in the race and I suspect the balls cover them alternately so a slow feed of grease should do well.

 

[Scott06]

Glad to help, I've always loved tearing things apart too. After seeing how the bearing is designed I've decided to grease it while it's running. There are 2 holes in the race and I suspect the balls cover them alternately so a slow feed of grease should do well.

Yes absolutely grease it while idling

In the old days you could just flip the bearing 90 degrees in the outer carrier to replace but merc started installing them the other way around to prevent this

 

[Lou C]

Greasing it when it’s running is a good idea just like jacking up & spinning trailer wheels when you grease em…it spreads the grease out optimally. Alternatively you could grease the gimble with the drive off and turning the inner race by hand…messy but you can feel how smooth the bearing is turning which is good to know as well….

 

[Rivergator]

I am just toying with the idea to pull out the bearing that's in my boat now which is the sealed type. The bearing is a good and solid bearing but my gut feeling tells me it's starving for some grease. Wouldn't it be something if the so called sealed bearing actually has the grease holes in the outer race and the only thing that's missing is the grease hole in the carrier ring, which therefore makes it a non-greaseable bearing. I am tempted to find out.

 

[nola mike]

I am just toying with the idea to pull out the bearing that's in my boat now which is the sealed type. The bearing is a good and solid bearing but my gut feeling tells me it's starving for some grease. Wouldn't it be something if the so called sealed bearing actually has the grease holes in the outer race and the only thing that's missing is the grease hole in the carrier ring, which therefore makes it a non-greaseable bearing. I am tempted to find out.

I mean, it wouldn't be sealed at that point. Curious if anyone has actually had a quality sealed unit fail without water intrusion. Theoretically should be more resistant to water as well.

 

[Rivergator]

I am just toying with the idea to pull out the bearing that's in my boat now which is the sealed type. The bearing is a good and solid bearing but my gut feeling tells me it's starving for some grease. Wouldn't it be something if the so called sealed bearing actually has the grease holes in the outer race and the only thing that's missing is the grease hole in the carrier ring, which therefore makes it a non-greaseable bearing. I am tempted to find out.

Well today I pulled my sealed gimbal bearing to satisfy my own curiosity and here is what I found. The sealed bearings are definitely sealed and do not have any holes in the outer race or grooves in the carrier ring like the greaseable ones do. Also the bearing swiveled nicely and I removed it from the carrier to see if I could come up with a way to repack the bearing. And yes, if you want to do that, you can. With the bearing out of the carrier and conveniently on my bench I was able to pop one of the side skirts off and repacked the bearing to my heart's desire. Then I pressed the skirt back on using a ring of the correct size that pushed the skirt back in to the outer race. The question is, is it worth it, because gimbal bearings are not that expensive. I look at them as consumable items that I will check every time I take the drive off and replace if needed, so I usually buy cheap aftermarket bearings which are usually just as good as the expensive ones.

 

[tpenfield]

@Rivergator When you exposed the bearing for re-packing was there a decent amount of grease in it? or did it look a little shy?

I think that is an issue with non-greasable bearings is that they don't always have enough grease in them to start. I also am wondering if those of use who have the outdrives/transom assemblies that are of the non-greaseable type, if we get the greaseable bearing just to be able to 'load it up' with grease prior to installation

Thank you for posting this topic, good stuff to think about.

 

[Rivergator]

tpenfield, it was a little shy of what a packed bearing should be, but not as bad as I expected it. I cleaned it out and repacked it. Now it is smooth and has a nice drag to it. Also something else came to my mind. When I look at the pics that flashback posted, where you can clearly see how the bearing gets its grease, if you ever have a greaseable bearing that doesn't seem to accept any grease, it's probably because it is facing the wrong side. I will now make it a habit to check any new greaseable gimbal bearing before installing it by swiveling it out of the carrier to make sure that the grease holes in the outer race are on the same side as the grease groove in the carrier ring is. And another thing. Why do the 2 cut outs in the carrier have to face the bow??? Chris, can you chime in on this? If they would face the rear it would be so much easier to replace a bad gimbal bearing. The carrier doesn't really wear and could stay in the housing. Turn the bad bearing 90 degrees pull it out and put in another one. Job done. Using a sledge hammer to drive in a complete new bearing is kinda rough on the housing and the transom seems like, isn't it? I know that's how its done unless you do it the super right way and remove the housing from the transom and press the bearing in.

 

[nola mike]

. Why do the 2 cut outs in the carrier have to face the bow??? Chris, can you chime in on this? If they would face the rear it would be so much easier to replace a bad gimbal bearing. The carrier doesn't really wear and could stay in the housing. Turn the bad bearing 90 degrees pull it out and put in another one.

You can put in the bearing either way. Merc specified it the way it is so that the bearing and carrier would have to be replaced as a unit. Apparently people were just replacing the bearing and they were failing prematurely. That's the rumor anyway. Dunno if it's true.

 

[Rivergator]

Nola Mike, I had a feeling that was the reason as I mentioned in my previous post. It would be a lot easier and less abusive to just change the bearing. As long as there is no play between the bearing and the carrier ring I don't see how this would lead to premature failure. Thanks for the explanation. I may or may not do it in the future, because it's not a big deal to replace the whole thing, especially when you use that nice smooth puller instead of a slide hammer to get it out. Putting it back was not too difficult either. After leaving the bearing in the freezer over night I hammered it back in and it all went quickly and without any problems. I wish everything would go that smoothly.

 

[flashback]

I'm going to guess that in some cases a bad bearing could seize and possibly spin in the carrier. The one in the pic I posted shows possible signs of that. IDK.

 

[harringtondav]

The problem that I have found is that there is typically not enough grease added to the bearings during the manufacturing process, so the bearing has a shorter life than it possibly could.

Agree. I've inspected new OEM 'Permalube' U joints before installation. They had a dab of grease in each race/cup. Easy enough to swap the pipe plug with a zerk and finish the job.
Having said this, I kinda follow Bondo's grease theory. It doesn't take that much grease to keep the needed film between the balls/needles and the races. Assuming the drive shaft assy is kept dry and operated sanely (no WOT donuts or figure 8's), Unis and gimbal bearings should last indefinitely.
Packing bearings until the grease shows itself may be a feel good, but I don't think it does that much extra good. It can be counterproductive with Unis if the seal is displaced from its groove.