Hi jchoquette! If the problem is the hole (s) in the butterfly try to solder them that way you dont have to replace the carb, the other thing is try a bigger prop (16x8) usually APC props are the best performance wise, I think that a 15x7 is very small and not putting enough load on the engine, there are other tricks to make your engine get higher rpms at the high end of the throttle like making the venturi hole in the carb bigger (0.400 inch diameter) just make sure not to damage the bronze fitting sticking out cut around it you can use an xacto knife to churn off the aluminum until you reach the diameter desired; or simply go and buy a bigger carb for it.