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Drive shaft housing and gear assembly compatibility

G

Ghg

Contributing Member
Hi, I have a 67 Mercruiser 120, the lower gear housing assembly has a crack from being frozen, the crack is on the bottom near the drain plug. Is this repairable? I have located another gear housing assembly from a later year, I think it’s a 1970’s or newer. Will this unit be compatible with my drive shaft housing?
 
Depending on the magnitude of the crack it may be repairable... given the age, its probably not worth the effort.

On the 'potential replacement unit' , "...1970's or newer..." is too broad to say for sure - if its pre-Alpha, it should be fine...
 
1967 thru 1969 (& some early build 1970) model #1 drives had a prop shaft with a square shoulder vs tapered for thrust hub, course threads & 10 spline vertical drive shaft. All later drives thru Alpha gen 1 (1990) had tapered prop shaft, fine threads & 13 splines.
So, if you have the original #1 drive, you cannot swap the bottom end only. You can however swap the entire drive.
 
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