'71 Johnson 85-125 HP power head

[Mouse1]

Trying to answer a question about a '71 V4 Johnson. Someone is selling a '71 85 HP and stated that the only difference between an 85 and 125 was the carbs.
Thought there has to be more than that because they have different part numbers.
Asking because my 125 block has a damaged cylinder and need a replacement.

 

[racerone]

The 85 is a smaller bore engine and thus less displacement !!----Your location ?

 

[Mouse1]

Located outside of Birmingham, AL.
Common sense told me there was a difference, but didn't know what.
When in doubt, ask the experts. Thank you.