I have a new MVVS 58cc that has 2 gallons of fuel through it at this time. I am running a NX 24X8 prop, but it is turning to many rpm's on the ground. 7830 rpm's on the ground, no telling what in the air. What I need to know is what size prop do I need to get the rpm's down to where they need to be. These props are too expensive to experiment with to find the right size. Also, NX does not make a 25" diameter prop, they go from 24" to 26". I was thinking of trying the 24X10 but I don't think it will drop the rpm's that much. I do know one thing, this is one powerful engine!!! I am really happy with it, it cranks easily and runs great. Has not dead sticked me yet.