MC-1 Drive Dog failure?

ratdude747 said:

How much more work we talking? When I had the drive apart to do the impeller last spring (2024) I don't recall that portion of the shifter feeling particularly sloppy.

Edit- nah, I'll check it when apart. If it it all is suspect, I'll replace. But if not, I'm reading it can be a royal pain to get the shaft out.

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You can use a length of threaded rod and some nuts and washers to make a puller to pull and press the bushings out and the new ones in, not too bad.. the tough part is the arm with the roller at the top. The set screw can be impossible to remove with corrosion and it's easier to split it with a hammer and chisel and replace it with new.
I'd add a tube of 2-4-C grease to the list.

Candy Gramformongo said:

I replaced my cable last summer. '76 MC-1. Had the old style cable. Tapped the hole and installed the new style cable.

Had the old style shift shaft bushing, replaced that too. The old style seal on it was not a very good design and yours is probably failed or failing, which causes bad things. They went to the new style for a reason. You'll probably have to destroy the aluminum shift lever to get it off. This sounds scary and like a lot of work, but it's not. Cheap part. Drill some small pilot holes on either side of the set screw hole, and it will crack right off with a couple of firm chisel whacks.

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Eric 3.7LX Alpha 1 said:

You can use a length of threaded rod and some nuts and washers to make a puller to pull and press the bushings out and the new ones in, not too bad.. the tough part is the arm with the roller at the top. The set screw can be impossible to remove with corrosion and it's easier to split it with a hammer and chisel and replace it with new.
I'd add a tube of 2-4-C grease to the list.

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Gotcha. Ordered Quicksilver 45518T1 which is a kit with the bushings and the lever. The lever roller may be shot anyway with as sloppy as my shifting was.

Grease: I have a grease gun with marine rated grease in it that I use for the zerks on the outdrive. That's what I planned on using for the cable.

ratdude747 said:

Gotcha. Ordered Quicksilver 45518T1 which is a kit with the bushings and the lever. The lever roller may be shot anyway with as sloppy as my shifting was.

Grease: I have a grease gun with marine rated grease in it that I use for the zerks on the outdrive. That's what I planned on using for the cable.

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That's the part. The one that's difficult is the shift shaft seal beneath the water pump in the drive, that may be the one that you were looking at.

nola mike said:

That's the part. The one that's difficult is the shift shaft seal beneath the water pump in the drive, that may be the one that you were looking at.

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Yep... the one that uses a special "prong socket" and is threaded.

This job just got a lot deeper. As soon as I broke the seal, oil started dripping out:



Once removed, it was a water-oil mess everywhere:



Tracing the oil, it leads up to the bottom of the input seal... so that's probably wasted:



(The U-joint, on the other hand, feels good, not tight and if there is play, it's too faint to really notice)

The shift cable/upper shaft didn't have much play and actually looked decent (although still the older design):


But... I did find the play. Lower shift shaft upper bushing is beyond wasted:


View attachment de77e707-1c7e-488b-913b-55c7a252e9a9.mp4

So, what am I looking at? An input bearing seal and the lower unit shift bushing of doom? Or are there other parts likely roached too? Looks like doing all the seals is a job to put it lightly... maybe look for a used Alpha 1 gen 1 drive in better shape for now and rebuild this one in the offseason?

Also, I'll probably need to try again on the bellhousing gasket. The kit included the alpha 1 gen 2 gasket with the extra hole... but since the hole passes through an exposed area, am I correct in that I probably couldn't trim the new gasket to match the gap between the upper and middle studs?

I don't see an issue with the shift foot play/slop

alldodge said:

I don't see an issue with the shift foot play/slop

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That's normal?!? Edit- duh- the foot drives the torx shaft in the lower unit, the seal's in the lower.

So maybe just need to do upper case seals? Would that seal going bad explain all the oil?

Most likely it was the upper drive shaft seal

Add the gimbal bearing to the list... spins freely but is lightly crunchy. May explain the seal failure (and/or made the failure worse). I have a boating coworker who has the special tools for such (alignment bar and bearing puller) so I'm good there.

As far as I can tell the drive shaft bearing is good. Just a bad seal.

As for the other things I've got on order:

• Quicksilver upper case seal kit
• Bearing retainer tool
• Sierra greasable gimbal bearing
• Quicksilver gimbal bearing seal
• 0-180 Inch-oz dial torque wrench (vintage eBay find for $42 shipped, but for setting preload should be perfect. If I ever do a full rear end on a vehicle I'll need it anyway)

I also went ahead and pulled the upper shift shaft. For those reading this in the future, I did have to cut off the shift lever... but the reason wasn't corrosion (rather, what appears to be factory red loctite!). I did this using a oscillatory saw and a hammer/chisel:



More pics of things while doing some more prep work...

Here's the lake of leaked gear oil in the drive bellows:



(At this point is where I checked the gimbal bearing and found that it was pretty much pooched)

More of that mess on the drive side. Why I'm very sure it's the u joint seal that's the problem:



Here's my cheating setup using a "hoyer lifter" and the lifting eye that old drives like this happen to have:



Like the draining at the start of the season, streaks of milkshake in the drive oil. At least I now know where it's coming from:



The only other variables I see are any bearing misalignment (We shall see, I had to mallet the drive out at first but once the O-rings cleared the shaft pulled out without much fight) and the condition of the U-joint yoke's sealing surface; until I have the tool and can get the retainer out, I won't know. I do have lathe access via work (and via father-in-law) if it just needs polished but if that's also pooched, then sleeve it or replace it?

Speedi Sleeve 99227 if you go that route. Mine had a groove that would not have polished out, and I bet yours will too. You don't even have to break off the installation flange.

Doing more reading, apparently the older drives (Alpha 1 gen 1 and earlier) don't use crush sleeves or rolling torque and instead use 200ftlb on the nut? Is this accurate?

You got a lot going on.
--Input shaft seal is responsible for the oil in the bellows. Where is the water coming from in the bellows? That could possibly be the reason for the water in the oil as well
--i don't think you need to set preload on an mc1, someone correct my if I'm wrong
--as mentioned the input shaft can have a speedy sleeve applied. Also possible to seat the seal so that it's sitting on a different portion of the shaft.
--pressure test the drive when you're done. Not sure if you can test the halves independently on an mc-1
--upper and lower drive shaft seals are accessible fairly easily once you remove the input shaft, wouldn't be a bad idea to replace those anyway. Get a dedicated bearing removal / insulation tool, $20 Amazon
--the extra hole in the gasket is for a Gen 2, at least on a gen one it doesn't cause any issues

nola mike said:

You got a lot going on.
--Input shaft seal is responsible for the oil in the bellows. Where is the water coming from in the bellows? That could possibly be the reason for the water in the oil as well
--i don't think you need to set preload on an mc1, someone correct my if I'm wrong
--as mentioned the input shaft can have a speedy sleeve applied. Also possible to seat the seal so that it's sitting on a different portion of the shaft.
--pressure test the drive when you're done. Not sure if you can test the halves independently on an mc-1
--upper and lower drive shaft seals are accessible fairly easily once you remove the input shaft, wouldn't be a bad idea to replace those anyway. Get a dedicated bearing removal / insulation tool, $20 Amazon
--the extra hole in the gasket is for a Gen 2, at least on a gen one it doesn't cause any issues

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My 1979 drive has spacers between the opposing tapered bearings. Preload is set by shimming O.D. and I.D. spacers then torquing nut. I don't know when the change went to "Rolling" torque.

The water entered the bell housing through the large rubber seal that was not glued inside of the bell housing. You must use 3M or the equivalent to hold the seal in place otherwise it gets dragged out of place and you will not know it, sometimes water will come into the boat.
From the picture the seal looks chewed up from the joints.
2.25” should be the size Speedy Sleeve you will need for the yoke.
That hoist is the best way to R&R a drive.

Coworker loaned me the gimbal tools. Pulled the bearing this evening. It clearly isn't original (as it's the later retainer style, not the original snap ring style). But it had been receiving grease from the zerk, so at least that part was working correctly. Did not remove the seal as I couldn't get purchase with the puller (but despite my attempts at removal, it seems OK, so I may let that be since it's just to keep grease from puking everywhere, right?)

Doing some investigating... a lot of sediment in the u-joint bellows and under the shifter once the oil was soaked up overnight. And I found dry rot starting in the exhaust bellows... the u-joint bellows seem to be fine other than the sediment. Since Mercruiser sells them as separate parts (and I already have a new shift bellows as part of the cable kit), I figure I'll just replace the exhaust... if it ain't broke, don't fix it?

kenny nunez said:

The water entered the bell housing through the large rubber seal that was not glued inside of the bell housing. You must use 3M or the equivalent to hold the seal in place otherwise it gets dragged out of place and you will not know it, sometimes water will come into the boat.

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Understood. Which 3M? 5200? I have some UV4000 leftover from recaulking rub rails this spring... but I assume that's not what's needed here.

kenny nunez said:

2.25” should be the size Speedy Sleeve you will need for the yoke.

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Am I safe to assume that the yoke is pooched and will need the sleeve?

Some people will change the ujoint bellows and leave the exhaust alone which would explain why yours is cracked. It's not as critical since the exhaust fills with water when the engine is shut off anyways. Some people run an exhaust tube instead of the bellows. I've always replaced all of them as a set when I did mine.

Eric 3.7LX Alpha 1 said:

Some people will change the ujoint bellows and leave the exhaust alone which would explain why yours is cracked. It's not as critical since the exhaust fills with water when the engine is shut off anyways. Some people run an exhaust tube instead of the bellows. I've always replaced all of them as a set when I did mine.

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Ah. So likewise, I'm not off my rocker for only doing the shift and exhaust bellows... honestly the shift may be OK but since I have the part in hand, I might as well?

Per a chat with a previous operator (Brother-in-law of the previous owner who did a lot of the maintenance on it), this sort of work was stuff they farmed out to a marina. A marina that messed the boat up... so this would be on point.

Definitely want bellows for the exhaust, as it stretches the most with trim movements.

The 3M product is for gluing the rubber to the edges of auto doors. A K A Gorilla snot.

kenny nunez said:

The 3M product is for gluing the rubber to the edges of auto doors. A K A Gorilla snot.

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I've always used permatex without issue.