1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 25Get this manual
dSet the motor idle speed to the specified level by adjusting the throttle stop screwTurning the throttle stop screw in (clockwise) increases the motor speed; turning it out (counterclockwise) decreases the motor speedUse tachometer for checking and adjusting the motor speedIdle speed: 900 50 rlmin
Replace the gear oil after the first 10 hours of operation and check the oil every 100 hours thereafter
BATTERY (for electric motor) 1The fluid level should be between the upper and lower level marksUse only distilled water if refilling is necessary
GEAR OIL Oil level check Remove the oil level plug and check whether the oil level is up to the bottom brim of the holeIf it is not up to this level, replenish oilNOTE: Be sure the motor is positioned straight up when checking the oil level
1Upper level
2Lower level