1973 Evinrude Norseman 40 HP Service Manual, Page 64Get this manual
There are instances where the propeller selected cannot cover the complete range of boat applications, for example, from water skiing to high speed performanceIn such cases it may be necessary to change propellers to suit each particular situation(Light load, higher pitch propeller; heavy load, lower pitch propeller Remember, if the motor operates below the recommended full throttle RPM range, motor is laboring and power and efficiency are being lostIf the motor operates above the recommended full throttle RPM range, motor speed is excessive and additional power and efficiency are not being
gainedresult
In either case, serious engine damage may