I would be interested in knowing that answer to question myself. I have a 1986 24 ft Riveria Crusier that I would like to put a Evinrude 115 on it. It has a Johnson 70 HP on it now. I have no idea what it's rated for as the rating plate is missing. My logs measure 19.25" in diameter so I would assume that has something to do with the maximum horsepower too?? How do you go about determining the maximum horsepower to start with???
Les, your toon was originally rated for 90 HP. I would check with your insurance company to see if they would cover you just in case if you put the 115 on..
Pics of your motor mount I can answer that, is there not a tag above the right toon? mine is a 24 footer with the adjustable mount, and it too is an oldie but goodie from 1964, and I am running a 75hp johnson