I used an OS 91 in mine and it is a shoe in fit but once in it's great. I liked the 91 because I could use a 3 bladed prop efficiently, I don't like them on 2 strokes but then I haven't really tried hard. A friend had a 60 2 stroke in his and it was fine I just liked the way mine could drop in when I pulled back on the power. ENJOY !!! RED