Propeller Replacement Propeller Dia (In.) 24 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 1/4 hp Required HP @ Lower RPM 1/12 hp RPM Low 800 RPM RPM High 1 075 RPM Max RPM 1140 CFM @ 0.000-In. SP 3950/2939 CFM @ 0.125-In. SP 3377/2255 CFM @ 0.250-In. SP 2912/1588 CFM @ 0.375-In. SP - CFM @ 0.500-In. SP - Blade Height (In.) 4 1/2 in