I've a 1974 70 HP Johnson and the middle pot has had some detonation damage to the top of the piston and cylinder head. The bore is also scored but would probably clean up on first or second oversize. The center crank pin is also damaged.
Is it possible to transplant a later powerhead from say 1990 upwards? I believe the splines on the drive shaft are different but what year did they change and could I change the drive shaft in my lower unit to match?
Any help would be appreciated. Cheers