Lower Unit interchange - '71, 25hp Johnson with '77, 25hp Evinrude

[84toyota]

I'm trying to determine whether I can swap lower units between a 1971, 25hp Johnson and a 1977, 25hp Evinrude motor. Both are short shafts, and both appear to be the same externally. I seem to find conflicting info when looking at various parts diagrams with part numbers for each lower unit. I've found some information stating that all lower units between 1969-1978 can interchange. Can anyone lend any further guidance? I'm concerned mostly with gear splines meshing up properly and lower unit gearing being compatible.

Thanks,
Ken

 

[Daviet]

Re: Lower Unit interchange - '71, 25hp Johnson with '77, 25hp Evinrude

You might check the "Top Secret Files" sticky at the top of the page, I think there is an interchange guide in there.

 

[hidef]

Re: Lower Unit interchange - '71, 25hp Johnson with '77, 25hp Evinrude

The lower units are interchangeable. The main parts you want to look at are the drive shafts, pinion gear and casings and they are the same for a 1971 and a 1977.