IF I was the designer, for ease of installation, I'd make it the same size as the others. Without a manual or a diffinitive answer here, I guess your at the trial and error phase. Try one of the other bolts. If it works, leave it there and move on. The others are easier to get to.
1989 Force 85hp dont have the model number but have been using h0858xh9h
So far the parts have been sortof correct except for the little reproduction of the bellows under the water pump houseing you have to buy a new kit, they dont sell the replacement seal anymore...