Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 379Get this manual
SELECTION Selection of the optimum propeller in regards to boat characteristics and outboard motor performance is of utmost importanceTo ensure smooth acceleration, top speed, smooth handling and good fuel economy, select propeller which is designed for your boat size and outboard motor outputConfirm that the boat reaches its speed at throttle and the maximum engine speedDESIRABLE PROPELLER CHARACTERISTICS
Advanced Distance during One Turn
(Visual Advanced Distance)
P: Pitch (mm) D: Outer Diameter of Propeller
P Pitch RatioD Slip Ratio
Visual Advanced DistanceMeasured Distance 100 Visual Advanced Distance During running the actually advanced distance is reduced by about 1015 due propeller display pitch