2004 SR Johnson 2-stroke 40, 50HP Service Manual, Page 56Get this manual
INSTALLATION AND PREDELIVERY PROPELLER SELECTION
PROPELLER SELECTION
Refer to PROPELLER on p234 before installing propellerThe correct propeller, under normal load conditions, will allow the engine to run near the midpoint of the RPM operating range at full throttleRefer to TECHNICAL DATA on p26
Procedure
The propeller selection process is very important to the engine's service life and to boat performanceProceed carefully and thoroughly while considering the following points: During the engine break-in period, run the outboard at wide-open throttle for only brief periods of time to check full-throttle RPM Use an accurate tachometer to determine the engine's full-throttle RPM while testing various propellers Select propeller that suits the customer's application and allows the engine to run near the midpoint of the full-throttle operating range when the boat has normal load in itRefer to TECHNICAL DATA on page 26 To compensate for changes in boat loading, the engine's full-throttle RPM must be verified periodically Occasionally, one propeller will not cover wide range of boat applicationswater skiing to high speed performance boatingIn such cases, it might be necessary to have propeller for each situation