Mercury Force 9.9, 15HP Outboards Service Manual, Page 40Get this manual
HADJUSTING IDLE MIXTURE IMPORTANT When adjusting the idle mixture screw, turn carefully and gentlyDo not force needle into seat1Turn idle mixture screw clockwise until it seats in the carburetor2Open id le mixture screw one turn (counterclockwise)
Start motor and allow to warm up to ope rating temperature Move throttle lever toSHIFT" position Shift motor intoFORWARD" gear and turn idle mi xture screw clockwise (close) to the lowestrunablesetting
6Slowly turn idle mixture screw counterclockwise until motor speed decreases and operation becomes rough due to over rich mixture (note adjustment position)7Slowly turn idle mixture screw clockwise: motor operation will become smooth and speed will increaseContinue turni ng idle mixture screw clockwise until motor speed slows or misfires from too lean mixture8Turn idle mixture screw to midpoint between settings noted in steps and 7