Propeller Replacement Propeller Dia (In.) 20 in Bore Dia (In.) 1/2 in Number of Blades 3 Pitch (Deg.) 20 Degrees Blade Material Aluminum Keyway (In.) - Rotation CW Facing Discharge Required Motor HP - Required HP @ Higher RPM 1/3 hp Required HP @ Lower RPM 1/10 hp RPM Low 1 140 RPM RPM High 1 725 RPM Max RPM 1725 CFM @ 0.000-In. SP 3766/2489 CFM @ 0.125-In. SP 3587/2183 CFM @ 0.250-In. SP 3375/1574 CFM @ 0.375-In. SP - CFM @ 0.500-In. SP - Blade Height (In.) 3 7/16 in