My Windy is 23" and the .10 makes it go really well. I am, however, building a new one with a .15. I will soon begin a Big Swamp Buggy that will have a .46. One of our local airboaters has a Big Swamp Buggy with a .54 four stroke. I know my new .46 has more power than his old Enya but his goes pretty well. I'll give it a try but build it so I can move up to a .52 or a .60. If my Windy is anything to measure by a .46 on a 23" hull is way too big. I'd go for a .25 but a lot depends on the design of the hull.