Using parts of a 1974 85hp on a 1973 115hp

[wojciecj]

I have a 1973 johnson 115 with a bad lower unit. I thought I would buy a parts motor to use the lower unit. Correct me if I'm wrong but would any lower unit from a 85-135hp johnson/evinrude from 1973-1979 work? I also don't know if the block is the same size on this motor range. Having a parts motor would I only be able to use the electronic components or are parts such as the cylinder heads the same? I just don't know what causes the horsepower change between the 85, 115, and 135. Is the bore slightly larger, are the carbs larger or both?

 

[boobie]

1973-1977 will work.

 

[Hooligan Diver]

I was able to use the lower unit from an '87 150 on my '79 235. Both being V6, and between crossover years '79-'91. I would think up to '78 would work, but I'd cross reference that to be certain before spending any cash...

 

[wojciecj]

Thanks for the replies. Are all the cylinder heads interchangeable between 85-135hp?