Stern drive woes

[HPwannabe]

Hi all,
Among the things I didn’t think I’d have to worry too much about, I’m now finding that my stern drive is perhaps in need of a lot of work. This is an alpha 1 gen 1, around 1984. First thing is the lower unit. Ive removed the water pump and when I turn the driveshaft I get a sound that I don’t like at all. There is also some very rough feeling to the shaft as I turn it. And there seems to be a little sideways slop in it. I am attempting to attach a video. If that doesn’t work, just suffice to say I don’t think I put this unit back into service without stripping it down. I’ve never rebuilt a lower unit before but it doesn’t look like rocket science. My biggest concerns are things like shimming and pre-load. I’ll take all the tips and advice I can get, along with links to the best instructional videos (I have a Seloc manual). Also note in the photos that the upper part of the shift shaft bushing has fallen apart, which I think might have occurred due to freezing. One thing I noticed is that the volume forward of the shaft has clogged up and wasn’t draining out of the weep hole, so maybe I got some freeze breaking of the bushing? What other issues might cause it to disintegrate like that?
The other issue is that The upper gear case seems tight. That gearcase has been rebuilt before. It takes a fair bit of effort to turn it, though it seems fairly smooth. Is there a guideline of how much torque is too much to rotate the input shaft (with gearcase separated from the lower unit of course)?

 

[HPwannabe]

Another thing about the shift shaft bushing. The stainless washer that goes on there is deformed. It looks like maybe the unit was forced back onto the upper housing with the the shaft coupler misaligned and it deformed the washer and perhaps broke the bushing. I don’t know. As far as I know I’m the only person who has had this thing apart, but I’m not 100% sure of that. It sure looks like some excess pressure has been put on it, and that be the thing that caused failure.

 

[Bt Doctur]

the shift shaft bushing corroded in half. The threaded portion is still in the lower unit.
The drive uses a spacial tool to set it up but you also can turn the drive upside down to set backlash. That drive will feel funny if you turn the shaft , its meant to be forced upward. If you lift and turn it will be a lot smoother

 

[76SeaRay]

I have completely disassembled my whole drive, upper and lower units, and am starting the rebuild process right now on the lower unit. I ended up having to buy a new lower unit housing due to holes corroded through the side of my old one. I have also replaced the lower unit forward gear and reverse gear bearings. Mercruiser recommends starting shims for the forward bearing race at 0.020 inch shims and I have found in two used lower units that is what was installed. For the lower unit driveshaft, Mercruiser recommends starting with 0.015 inch shims.

I have video's that you can study/use. They are large files so I would need to send you a link to download them from Dropbox. PM me your email address if you want them. However, if you have to replace gears, you may find it cheaper to get a new unit or maybe the SEI Alpha replacement drive. As a minimum I recommend pulling the prop shaft assembly to see what your gears, bearings, and clutch dogs look like.

 

[76SeaRay]

Just watched your video, it sounds like to me that you have gear and/or bearing problems particularly with the amount of "wobble" in your driveshaft.

 

[HPwannabe]

the shift shaft bushing corroded in half. The threaded portion is still in the lower unit.
The drive uses a spacial tool to set it up but you also can turn the drive upside down to set backlash. That drive will feel funny if you turn the shaft , its meant to be forced upward. If you lift and turn it will be a lot smoother

Bt Doctor, yes, I noticed when I pulled up on it, it was reasonably smooth. But the logic in my head was "well, that's just because I pulled the bearing up off the race, so there's no contact anymore".
By the way, the unit has never had any oil leakage issues, had good oil fill prior to disassembly, and gets relatively little use. I don't want to break into this thing unless I have to, but maybe at least an inspection and seal replacement is in order.

 

[HPwannabe]

Just watched your video, it sounds like to me that you have gear and/or bearing problems particularly with the amount of "wobble" in your driveshaft.

The wobble bothered me too, but again, I don't know how much is tolerable. I'll pm you for those videos. Thanks.

 

[76SeaRay]

That upper drive shaft has both upper and lower bearings so should be pretty snug.

 

[HPwannabe]

So how do I get that bushing out of there now that it’s busted off?
Also, I double checked and when I lift up on the shaft it’s pretty darn smooth, and essentially all the play is gone. Is this normal? If so, what am I feeling when I press down and turn?
Anybody got any advice on the upper housing tightness? I think I definitely need to disassemble, replace seals, and double check shimming.

 

[76SeaRay]

Just had a thought, where is your shift shaft set, forward, reverse, neutral or just somewhere? The sound could be the dog clutch hitting but not engaging either the forward or reverse gear because the shifter is not all the way engaged or disengaged.

When you are moving the shaft around (wobble), you can see it is moving the bearing around. Bearings should always be seated snuggly in their races (bearing cup).

When it comes to the shift shaft bushing, pull the o-ring out and hit it with PB Blaster or your favorite. It is going to be tough to remove. You might be able to use the corner of a chisel or punch and drive it around to unscrew it. Worst case, you might have to drill small holes through it to see if you can break up the rest of the piece without damaging the threads. If you can't get it out, then its a new housing.

Word of caution if you get a new housing, there are at least two types and you have to make sure you get the right one. I got the wrong one on my first try and had to return it.

 

[HPwannabe]

So I got advice from my resident expert - my brother. The driveshaft is fine. I didn’t realize the direction of the thrust on this. It’s upward. So that’s one question answered.

 

[Rick Stephens]

So I got advice from my resident expert - my brother. The driveshaft is fine. I didn’t realize the direction of the thrust on this. It’s upward. So that’s one question answered.

You already had that answer in post #3, which you ignored.

 

[HPwannabe]

You already had that answer in post #3, which you ignored.

I didn't ignore it. I responded to it, and it was good advice. I still was not sure, from the information provided, whether there still might have been issues. It's always good to have someone who knows to actually put their hands on it. That gave me the confidence that it was in fact good to go.

 

[HPwannabe]

The big issue right now is getting the shift shaft bushing out (the top corroded off). Any tricks or tips are appreciated. I think I might wind up drilling a bunch of small holes, and then just bust out the pieces. Only problem with that is that is going to result in lots of metal going into the gearbox (unless I can figure out how to do it upside down).

 

[kenny nunez]

If you are worried about drill chips in the lower then try this.
Below the bushing is a flat washer with a hair pin clip or another type of retainer. With 2 pair of vice grips biting the shift shaft splines pry up and the clip will either break or open enough to pull the shaft out then with a Easy out you should be able to unscrew the bushing. The clip and washer can be fished out with a small magnet.
Before the stainless steel shift shafts came out it was pretty common that clip would slip and the shaft would come out because it was rusted in the brass lever when the lower was dropped to replace the water pump.
Also you could try drilling 2 holes with a 3/16” bit close to the shaft then with a 1/8” pin punch you might be able to also knock the retainer down enough to pull the shaft.

 

[HPwannabe]

If you are worried about drill chips in the lower then try this.
Below the bushing is a flat washer with a hair pin clip or another type of retainer. With 2 pair of vice grips biting the shift shaft splines pry up and the clip will either break or open enough to pull the shaft out then with a Easy out you should be able to unscrew the bushing. The clip and washer can be fished out with a small magnet.
Before the stainless steel shift shafts came out it was pretty common that clip would slip and the shaft would come out because it was rusted in the brass lever when the lower was dropped to replace the water pump.
Also you could try drilling 2 holes with a 3/16” bit close to the shaft then with a 1/8” pin punch you might be able to also knock the retainer down enough to pull the shaft.

Thanks Kenny that’s great info. Here’s what I’ve done so far. Drilled a bunch of holes. Then tried unscrewing with large needle nose, twisting with a wrench while tapping on the wrench. No joy. I’m now working on it with a dremmel. Your method sounds worth a shot.

 

[HPwannabe]

The dremel did the trick. I think the housing was spared, but I’m gonna need to chase the threads, and clean up the chamfer. Anybody know what size threads these are?

 

[76SeaRay]

Congrats on getting it out. You are going to have a tough time getting the shift shaft inserted back into the shift spool C arm. You might get lucky and it will stay aligned but I am guessing it will probably have leaned to the side and may even have disengaged the spool slot. Make sure you check proper shift operation when and if you get the shaft engaged..

 

[kenny nunez]

You do not have to worry about reinstalling the shift shaft. There is no way the “C” shaped lever can come dislodged. The entire propeller shaft has to be removed before before the lever can be removed.

 

[HPwannabe]

Yeah, I eyeballed it and it looks lined up properly. Probably gonna get a new shaft, as I did get against it with the dremel and scuffed it. Again if anyone knows that thread size appreciate a heads up.
Thank you all for your advice so far on this thing.