Mercury Optimax Models 135, 150, Direct Fuel Injection., Page 24Get this manual
GENERAL INFORMATION
To obtain optimum engine performance under changing weather conditions, the engine MUST be propped to allow it to operate at or near the top end of the recommended maximum RPM range at wide-open-throttle with normal boat loadThis will allow the engine to develop full power while operating in an RPM range that discourages damaging detonation