Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 40Get this manual
TUNING the center, the bow will be light and the boat will "plane" more efficientlyFor this test the boat must be operated in body of waterCheck the engine rpm at full throttleThe rpm should be within the Specifications in the AppendixAll OMC engine model ser ial number identification plates indicate the horsepower rating and rpm range for the engineIf the rpm is not within specified range, propeller change may be in orderA higher pitch propeller will decrease rpm, and lower pitch propeller will increase rpmFor maximum low speed engine performance, the idle mixture and the idle rpm should be readjusted under actual operating conditions
bottom carefully for marine growth or evidence of "hook" or "rocker" in the bottomEither one of these conditions will greatly reduce performancePerformance