1975 Evinrude 40 HP Outboards Service Manual, PN 5093, Page 72Get this manual
PROPELLER SELECTION GENERAL Selection of the correct propeller is one of the most critical factors in achieving satisfactory performance of boat and motorPropellers must be custom selected to match the motor to the boat, load or application(SELECTION OF AN INCORRECT PROPELLER CAN CAUSE SERIOUS DAMAGE TO THE MOTOR When shipped from the factory, the motor is equipped with propeller that will give satisfactory performance under average conditionsHowever, since some boats have speed potentials that are quite high or low, it may be necessary to install propeller having an increased or decreased pitch and diameter to achieve maximum performanceOptional propellers are available to replace the propeller furnished with the motorSee Specifications, Section 2, for Propeller OptionsAluminum, bronze, cupped, and stainless steel propellers are also available as optional accessoriesSELECTING THE CORRECT PROPELLER Since propeller pitch and diameter determine motor RPM at given boat speed, the importance of correct propeller selection cannot be over emphasizedThe NOTES