Mercruiser Alpha 1 Gen 1 -- Gimbal bearing

[Ugarph1982]

Good evening,

I'm looking for a little advice on gimbal bearing installation. Quick context to question ... I have a 1988 Merc 3.7L tied to an Alpha 1 Gen 1. I've had the boat about 5 years and we run it quite a bit in the summer, and it has served us well. I have re-sealed the outdrive before (carrier bearing seal -- oil in bellows), I change the impeller and housing every 2 years, and I keep up with all of the routine maintenance.

Concerning the gimbal bearing ... I put in a new bearing 2 years ago when I changed out all of the bellows. I opted for one of the sealed units, rather than one that is serviced through the zerk, because it sits in the water all summer. I put the supplied plug in the zerk fitting.

Today we were out for an early season boat ride ... Got her fired up and accelerated for a test lap around the cove. About 60 seconds into the ride, some *major* bearing went to shrapnel. At first I thought it was a rod or crank bearing in the motor, but all oil pressure and temperature indications remained stable as I limped back to the dock. The boat was shifting fine as well, as I put it in reverse to dock it.

I believe that the gimbal bearing crapped out on me, given the deep moaning and roaring sound it was making. I'm actually hoping this is the case. I already pull the drive off every year to grease the u-joints and check alignment, so putting in another one should be easy-peasy. Once the drive is off, it will be easy to identify the motor, the stern drive itself, or the gimbal bearing.

The reason I'm posting here is for advice on installing the new gimbal bearing. When I installed the last one, I just wasn't satisfied with the seating of the bearing and alignment processes. I used an appropriately-sized seal driver to drive the bearing into place. Once it was seated, it took a fair amount of jimmy-ing it around with the alignment bar before I could easily slide the rod into the coupler. I felt like I was torquing the crap out of the bearing, and perhaps that's the reason that it (possibly) failed early. What advice does anyone have that has installed a million of these things?

My whole diatribe could be moot if I find out my mighty 3.7 has taken a dump ... In which case it will be the end of an era. I'm pretty confident in my gimbal theory, tho.

Thanks in advance!
Russ

 

[crazy charlie]

I recommend a standard gimbal bearing.I have never had one fail in over 30 years of stern drives.Grease in the spring,again in the fall upon seasonal hauling and again before launch.Zerks are good.They make/allow you depend on YOU.Not a bad thing.Charlie

 

[Rick Stephens]

Gimbal bearings 'gimbal'. That means they are aimable within their carrier. The first step in aligning a motor is to align the gimbal bearing so it aims at the coupler. THEN you can start checking the alignment, which is totally different thing than aiming the gimbal bearing. Alignment is up and down on the engine.

My recommendation is line up the gimbal bearing first by eyeballing it through to the coupler - aim it straight at the coupler. Then when the alignment bar can insert into the coupler, give the bar a good hard whack with your palm up, down, left and right. I actually use a deadblow hammer for this, others say your palm is enough. This will get the bearing straight on so you can go on to alignment checking.

I'm not sure most seal drivers are stiff enough to install a gimbal bearing easily. I guess, as long as it is substantial.

As far as your symptoms, spend the 15 minutes getting the drive off and see what you got before asking us to guess.

 

[Ugarph1982]

CC:
Thank you for your thoughts on the serviceable bearing. I like the idea of this as well. When I cross referenced the part from the diagram, it seems most of them had been superseded by sealed units, so I took the bait and tried it. I will be going back to a serviceable unit, assuming the one in there is bad.

Rick:
I appreciate your thoughts on the installation. The seal driver I used has a 1/4" steel backing plate for rigidity. I don't feel that it had any issues driving it into place. I put the bearing in the freezer for about 20 minutes, and several good strikes seated the bearing. I then used my palm to nudge the bar around to get the bar to slide into the coupler. My entire question stemmed around doing this, as I thought I might be damaging the bearing with the nudging.

Once getting it in, I had to give the alignment nut on the front of the engine about 1.5 turns for optimum alignment. Generally 1/4 and 1/2 turns each year get the alignment perfect. I expected a little more with a new installation.

I'm definitely not looking for internet diagnosis (or guessing) of the what has failed on my boat -- just advice on gimbal bearing installation, which you generously provided. I asked the question before diagnosis because I want to have the new bearing in hand before I take anything apart, so that I didn't have to wait for a new one to arrive with boat parts laying in the driveway. If the bearing is not what failed -- return to sender and boat to junkyard. I took the 3.7 out of the boat when I first bought it to sleeve the cam, and I have no intention on removing it again!

BTW, if it takes 15 minutes to get the drive off, you're slacking ;-) ... I am better than a 1-man NASCAR pit crew with that thing.

 

[achris]

Sound like you may have driven the bearing in on the inner race. If you did, that's why it failed. Have a look at my video on gimbal bearings...

Chris.

BTW. Agree with the 15 minute comment. My drive can be off in under 4.

 

[Ugarph1982]

Sound like you may have driven the bearing in on the inner race. If you did, that's why it failed. Have a look at my video on gimbal bearings...

Chris.

BTW. Agree with the 15 minute comment. My drive can be off in under 4.

Chris,

That's really a good and informative video on the bearing. I had no idea they were that flexible. That's some very good advice about installation.

When I was driving the bearing in, the seal driver I used was mated to the *outer* race. The main difference in my tool versus the correct specialized tool in your video is that mind did not have the inner centering billet. I took good care, though, to ensure the driver was centered on the outer race before each blow of the hammer. Maybe I wasn't as centered as I thought, our perhaps I put it in backwards?? It looks like my nudging with the hammer to get the alignment tool into the coupler was the correct approach.

I will check when I remove the drive. Right now, I've got to have the boat towed to the ramp to pull it out. Otherwise, I'd know my diagnosis by now. It will be interesting to see if I see a bunch of balls littering the inside of my drive bellows ... Hopefully, if it was the gimbal bearing that failed, it didn't damage the gimbal housing.

 

[Rick Stephens]

I think you are missing the point on a proper installation tool. The inner part of the gimbal bearing is taller than the carrier. If your driver is not relieved at that spot then you are pounding on the inner race and damaging the bearing rollers and race surfaces.

 

[Ugarph1982]

I think you are missing the point on a proper installation tool. The inner part of the gimbal bearing is taller than the carrier. If your driver is not relieved at that spot then you are pounding on the inner race and damaging the bearing rollers and race surfaces.

Thanks Rick. The driver is completely relieved in that spot and makes zero contact with the inner race. It looks exactly like the tool you pictured, except doesn't have the centering shaft to ensure the alignment with outer race. I've never seen that tool pictured (relieved driver with a set screw for alignment bar). I've always seen it as one piece. I'll see if I can find something like that reasonably priced to ensure correct installation.

 

[todhunter]

Thanks Rick. The driver is completely relieved in that spot and makes zero contact with the inner race. It looks exactly like the tool you pictured, except doesn't have the centering shaft to ensure the alignment with outer race. I've never seen that tool pictured (relieved driver with a set screw for alignment bar). I've always seen it as one piece. I'll see if I can find something like that reasonably priced to ensure correct installation.

I haven't used it yet, but I bought my gimbal bearing removal / installation / alignment tools from MBS Manufacturing on Amazon, and they look like the ones Rick has pictured above.

 

[Ugarph1982]

Little update here ... and a follow-up question.

Turns out that I had water intrusion into my drive bellows. Not enough to enter the boat through the gimbal bearing, but enough to cake the gimbal bearing and drive shaft in heavy rust sediment and corrode both of them all to hell. It was, in fact, the gimbal bearing that went to shrapnel.

I have replaced the gimbal bearing, and completely replaced the drive shaft (engine shaft into the coupler, u-joint cross bearings, connector, upper input shaft (using the full SEI assembly) and carrier bearing seal) ... so the the drive should be good as new. The oil in the drive looked perfect when I drained it. Changed the water pump housing and impeller while I was at it.

Because I can't tell exactly where the intrusion occurred, I've decided to replace the drive bellows. (and of course the bell housing gasket and usual maintenance rubber seals). I really think it came in through the mating surfaces on one end of the drive bellows.

My question is about the drive bellows and preparing the surfaces. I went against several seasoned mechanics who told me not to use the recommended quicksilver bellows adhesive, and I used it anyways. The stuff is the most awful nasty $h1t ever invented and I'm having a very tough time getting it off of the transom plate assembly and bell housing mating surfaces. What's the best way to clean that stuff off? I've tried engine degreaser and a scouring pad, but some still remains.

Needless to say, I will not be using the adhesive on this application. It makes it to difficult and tacky to seat the bellows that's already in tight quarters. I know that's kind of the point of the adhesive, but I believe it does more harm than good.

Thank you, in advance, for any input.

 

[achris]

If you scratch up the aluminium surfaces any, make sure you repaint, with a good etching primer. If you don't, that will be the next failure point. As for the adhesive, I have never installed a bellows without it. You don't have to use the Merc one (but I do), you can use weather strip sealer or (I think) 5200.

Chris......