Yamaha 90D Owner's Manual

Contents

Operation22motor greatly affects the water resistance. Ifthe mounting height is too high, cavitationtends to occur, thus reducing the propulsion;and if the propeller tips cut the air, the enginespeed will rise abnormally and cause the en-gine to overheat. If the mounting height is toolow, the water resistance will increase andthereby reduce engine efficiency. Mount theoutboard motor so that the anti-cavitationplate is in alignment with the bottom of theboat.NOTE: The optimum mounting height of the out-board motor is affected by the boat/motorcombination and the desired use. Testruns at different heights can help deter-mine the optimum mounting height. Con-sult your Yamaha dealer or boatmanufacturer for further information on de-termining the proper mounting height. For instructions on setting the trim angle ofthe outboard motor, see page 30.EMU27020Breaking in engineYour new engine requires a period of break-in to allow mating surfaces of moving parts towear in evenly. Correct break-in will help en-sure proper performance and longer enginelife.CAUTION:ECM00140 Failure to follow the break-in procedurecould result in reduced engine life oreven severe engine damage. Premix fuel must be used during break-in in addition to oil in the oil injectionsystem.EMU27060Gasoline and engine oil mixing chart(50:1)CAUTION:ECM00150Be sure to mix gasoline and oil complete-ly, otherwise the engine may be dam-aged.EMU30310Procedure for oil injection modelsRun the engine under load (in gear with apropeller installed) as follows.1. First 10 minutes:Run the engine at the lowest possiblespeed. A fast idle in neutral is best.2. Next 50 minutes:Do not exceed half throttle (approxi-mately 3000 r/min). Vary engine speedoccasionally. If you have an easy-plan-ing boat, accelerate at full throttle ontoplane, then immediately reduce theZMU017621. : Gasoline2. : Engine oil