An X447 is a pretty big prop for any of these motors man. If I were you, I would be starting with about an X440 and then working your way up. Once again the ammo motor is going to be a better choice, although if you intend to run a prop as big as a 47 then you might want to look at something a bit bigger and better as far as motor is concerned but then again, it will start to get quite expensive. I would be looking for a little less prop maybe an X445, that I know you can run an ammo and an SV27esc with a good 40mph on 12 cells.