14 x 8 is the prop this engine likes. Ifly with a XOAR 14 x 8 and have had an O.S. 91 in my Top Flite T-34, Direct Connection Sea Fury, KMPBlack Widow (2x) and all flew great with the 14 x 8. Turned just under 11k on the ground.

Flew at least 15 gallons of fuel through the O.S.'s in this config!</p>