I may need to shim the upper sterndrive questions.

[1985 Century Mustang]

When I recently removed the upper vertical shaft and the main drive shaft on Merc Alpha One Gen One to do the upper and lower seals, there were shims on both. I tried installing them back as best as possible, but noticed one shim was damaged, and I noticed that one of the the upper vertical shaft shims (under the cover) by the upper bushing was destroyed.

So, I need to re-shim everything again methinks, are these tools expensive to buy, and is it difficult to do as a newbie? I have an option to purchase an upper sterndrive for $200 and I may consider it today. The seller said the upper is in good working condition.

Further- I don't really see any good videos on YouTube to guide me, so I'm thinking maybe bringing it to a shop. If you guys have any good videos or pertinent info please post them. Your thoughts.

 

[ScottinAZ]

The tools are not going to be “cheap”, especially for a one time use deal. If it were mine, I would mike out the shims and replace with new. There should be someplace left on the shims that is flat enough to get a spec on them. OTOH, $200 for a “good working” upper may just be too good a deal to pass up. You will likely spend more than that on parts and tools, and surely more than that to take it to someone else to do it. Worst case, get the spare upper, and tinker with the busted one in the off season. A spare is just insurance against failure


As far as doing the job, I wouldn’t think it any more difficult than setting up a gear pattern on a rear end. In the end, it works the “same way” and pattern is needed to prevent wear. Access however will be different but the theory is the same

 

[dave8311]

Is that upper you might be buying the correct gear ratio?

 

[kenny nunez]

The lower bearing cup shim is what sets the lower gear. Upper shim
just sets the preload which is around 6-8 in“ lbs of rolling torque. If the recess in the cover is still good and the upper bearing cup fits snug then you just need to install the upper shims until the preload is set. Then install the driveshaft along with the shims. You do not need the shimming tools for this.
Is the surface on the lower gear good enough for the seal to hold pressure?
You may have to install a Speedy Sleeve over the area to restore the surface otherwise you will burn up another bearing and the gear set.

 

[1985 Century Mustang]

The tools are not going to be “cheap”, especially for a one time use deal. If it were mine, I would mike out the shims and replace with new. There should be someplace left on the shims that is flat enough to get a spec on them. OTOH, $200 for a “good working” upper may just be too good a deal to pass up. You will likely spend more than that on parts and tools, and surely more than that to take it to someone else to do it. Worst case, get the spare upper, and tinker with the busted one in the off season. A spare is just insurance against failure


As far as doing the job, I wouldn’t think it any more difficult than setting up a gear pattern on a rear end. In the end, it works the “same way” and pattern is needed to prevent wear. Access however will be different but the theory is the same

A few days ago I located a seller in Northern NJ on Facebook Marketplace that had an upper Merc Alpha One Gen One sterndrive for $200. It turns out the drive was only used in a freshwater lake in Lake Wallenpaupack PA, as he remembered the boat he yanked it from.

When I got there to his home in NJ to make the purchase, he said why don't you take the whole drive for $400, in which I did. He opened the top cover and there was clean gear oil in there, everything looked tight and intact,, all I wanted to see. The prop and u joint/shaft were in real minty condition too.

The seller had a lot of used drives, engines, boat trailers and some other parts for sale also, as he acquires/purchases used boats locally, then in turn repairs them and resells them. He had a pretty nice garage setup too for doing all his work and repairs. I was truly amazed.

A great guy, retired Jersey Trooper too. He told me if there are any issues he would take it back and or make good for it. A no brainer freshwater sterndrive for $400. Let's see how it goes. I may keep the drive intact or put my lower unit on it, as I just redid the water pump recently.Hopefully I'll be in the water this mid week.

 

[dave8311]

Once again, is that drive the correct gear ratio for your motor?

 

[1985 Century Mustang]

Once again, is that drive the correct gear ratio for your motor?

Very good question as I'm not 100% sure, this drive I just bought from the seller said it came off of an older 3.0 Merc, It's also an Alpha One Gen One. My engine is a 3.0L 140hp. Alpha One Gen One also. Hopefully it will work. Keeping my fingers crossed.

 

[1985 Century Mustang]

@dave8311 , judging by this chart It seems the common upper gear set is 1.94 gear ratio for the 1980s Engines 3.0 liter and 140 hp. I think I'm safe

Gear Chart - Sterndrive Replacement

Ratio Chart for Mercruiser sterndrive, alpha one generation I and alpha one generation II

www.sterndrivereplacement.com

 

[dave8311]

 

[1985 Century Mustang]

@dave8311 I'm going to use my original lower drive that i just rebuilt with the newer top drive that i just purchased, it seems they are both identical lower units. Is this a bad move, if i dont know what the lower gears are? Does it matter? They are exactly the same lower units, and both came off an 80s Mercruiser 3.0 Alpha One Gen One.

 

[ScottinAZ]

@dave8311 I'm going to use my original lower drive that i just rebuilt with the newer top drive that i just purchased, it seems they are both identical lower units. Is this a bad move, if i dont know what the lower gears are? Does it matter? They are exactly the same lower units, and both came off an 80s Mercruiser 3.0 Alpha One Gen One.

should be no issues. just dont lose that little o-ring

 

[1985 Century Mustang]

should be no issues. just dont lose that little o-ring

Roger that.