Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 380Get this manual
PRECAUTION WHEN SELECTING PROPELLER The outboard motor must be installed vertically in relation to the bottom of the boatProtect the propeller from foreign objects, and check regularly for damages and deformation, and aquatic plants wrapped around the propeller hubKeep the bottom of the boat clean from shells, algae growth and dirt (they will cause significant drop in top speed)When doing propeller checks select calm day with little wave actionAvoid strong winds; the wind speed should be less thanms (0.0010.002 mile&)The boat should carry its average load (crew, load arrangement, ballast)Perform the propeller check under the above conditions
TOP SPEED CANNOT BE REACHED AT FULL THROTTLE
In this case the propeller is not properly matchedLower the propeller pitch by one size (1inches), to avoid power loss and potential outboard motor damageIf it is necessary to lower the engine speed, select propeller with pitch one size largerIf the following cases occur, acceleration will improve and the life expectancy of the outboard motor will increase by lowering the propeller pitch- at heavy loads (Crew, load, equipment, water skiing, etcplaces with high temperatures and high humiditywhen using in higher elevationswhen the boat bottom needs cleaningwhen the area around the gear case is obstructedwhen there is propeller damageNOTE: Do not use full throttle, but run the outboard motor with 7080 of full throttle, to increase outboard motor life and to ensure safe navigation