Propeller Replacement Propeller Dia (In.) 18 in Bore Dia (In.) 1/2 in Number of Blades 3 Pitch (Deg.) 23 Degrees Blade Material Aluminum Keyway (In.) - Rotation CW Facing Discharge Required Motor HP - Required HP @ Higher RPM 1/4 hp Required HP @ Lower RPM 1/12 hp RPM Low 1 140 RPM RPM High 1 725 RPM Max RPM 1725 CFM @ 0.000-In. SP 3082/2037 CFM @ 0.125-In. SP 2842/1656 CFM @ 0.250-In. SP 2584/1331 CFM @ 0.375-In. SP - CFM @ 0.500-In. SP - Blade Height (In.) 3 3/4 in