Re: thinking about buying a boat with a 85hp 1984 I think
Even the best of motors run like crap if not taken care of. Probably fuel/carb related.
That would be a 3 cyl. carb motor, so expect to have to check/clean carbs, check for fuel/water seperator issues.
You can set up a small tank with fresh fuel and that will help to eliminate some of the problems. Try using our search function on how to decarb motors, using seafoam. Good luck!