dansy what kind of rpm #s are you getting with which props. Also what kind of pipe are you using. The latest numbers I got from piedmont models on the new webra 145 aero x was 8200rpm with an 18x10 mez. in 95% heat and high humidity. I am heavily considering this engine becuase of its light wieght 28oz and new AAr technology that helps disaipate heat.