I HAVE TO ASK..........why are you running that size of prop?..............you must only be getting 5500rpm or close to it?

Think of it this way............the bigger the prop the more the load on the engine.........the more the load on the engine the less the rpm.........the less the rpm the slower the big fan on the front turns.........the lslower the big fan turns the ess the cooling on the AIR COOLED motor.

If you have a noise problem put on a 3 blader