i have a '75 25hp 'rude and i was wondering what the differences were from the 35hp...is it just the carb? or compression ratio, bore stroke, different block, etc?
Completely different engine. Those two don't share the same block. The 35 hp was new for 1976 while the 25 hp was based on the old 18 hp. The 25 hp stepped up to the same block as the 35 hp in 1977 or 78 (I believe). Also, the 35 hp has thru-hub exhaust. Yours does not. The 25 hp didn't get that until 1985.
oh ok i knew there was a change somewhere but I wasnt sure what year. As for the thru hub exhaust: how similar are the lower units? If i got a 35 lower unit from a comparable year engine would it bolt up? I like the thru hub much better.
