Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 416Get this manual
HONDA BF25A
Before Selecting Propeller The following items must be checked and adjusted as necessaryThe outboard motor must be installed vertically in relation to the bottom of the boat (adjust the trim angle as needed to achieve proper boat plane)Adjust the trim tab, so that the boat has neutral steeringProtect the propeller from foreign objects, and check regularly for damage and deformation, and aquatic plants wrapped around the propeller hubKeep the bottom of the boat clean and free of algae and other growth (this 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 than 10 mileslh (15 kmh)The boat should carry its average load (crew, load arrangement)PITCH
Maximum Engine RPM Cannot Be Reached At Full Throttle The propeller may not be properly matched to the boatRun the boat up to full speed and check the engine rpmIf the engine rpm is above or below the maximum recommended engine rpm the propeller can be changed as follows: To avoid power loss and potentialoutboard motor damage do not exceed the maximum recommended engine rpmTo increase the engine rpm, select propeller with smaller pitchTo decrease the engine rpm, select propeller with larger pitch