tobyiscool82
New member
hi guys, i have a 73-77 merc 402 that runs awesome but it wont let me shift into reverse,,, so i bought a 80-81 merc 40 to switch lower units,, after getting both off i noticed that the smaller shaft the drives the water pump is bigger and has splines on the 80-81 the 402 lower unit only has a square top on it,, is thier any way i can make the 80-81 lower unit work on my 402