Swapping upper unit ring and pinion gears.

[Starcraft Enterprise]

Bought and mounted a really good condition 1981 MC-1 to replace my 1969 MC-1 that broke its lower drive shaft. Turns out the new MC-1 is either for a 6 cylinder or 3.7 4 cylinder, wrong ratio. Limped through last summer with a 14P prop. vs my stock 19P.

Can I swap out the ring and pinion from my 1969 MC-1 into my 1981 MC-1?

Is the upper unit from my 1969 MC-1 compatible with the lower unit from the 1981 MC-1 to make one good unit? I thought I remembered reading something about the oiling being different.

If they are not compatible, what year did they start being compatible with the 1981 MC-1? 1974?

1969 120 Mercruiser

 

[Don S]

Re: Swapping upper unit ring and pinion gears.

I doubt the internals are the same. There were small changes in gear sets and bearings from year to year. You would have to sit down and check out an oem parts site to see if the part numbers are the same between the two. They also change by serial number range, not year.
Your other problem is you would need to re-shim the gears for the different housing. Unless you have the special tools, you can't do it.

 

[Starcraft Enterprise]

Re: Swapping upper unit ring and pinion gears.

I doubt the internals are the same. There were small changes in gear sets and bearings from year to year. You would have to sit down and check out an oem parts site to see if the part numbers are the same between the two. They also change by serial number range, not year.
Your other problem is you would need to re-shim the gears for the different housing. Unless you have the special tools, you can't do it.

Was afraid of that. I am tired of playing this used junk swapping game anyways. For $650 I can get a brand new SEI 106 upper and go boating instead of wrenching. I think I will just go that route. Thanks for the help.

 

[TilliamWe]

Re: Swapping upper unit ring and pinion gears.

That's a good idea Starcraft.

 

[Bondo]

Re: Swapping upper unit ring and pinion gears.

Is the upper unit from my 1969 MC-1 compatible with the lower unit from the 1981 MC-1 to make one good unit? I thought I remembered reading something about the oiling being different.

Ayuh,.... I'm not sure 'bout the Oiling, but the spline count of the top of the vertical shaft is different,....

I think that change was mid-late-70s...