shaft length more important
Bob, have seen from 3.5 to 15 hp on the transom of C-22's, with alot of them around 5-6 hp. The 9.9 would let you push current and wind, but if it's rough and you are counting on it, get the 20 inch shaft for sure. I had a 7.5 Evinrude which was lots but with the short shaft it cavitated in rough stuff and we had to all sit in a pile port-aft to keep the prop in the water