2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 36Get this manual
PERIODIC MAINTENANCE IDLE SPEED
IDLE SPEED
INSPECT INITIALLY AFTER 10 HOURS (1 MONTH) AND EVERY 200 HOURS (12 MONTHS) THEREAFTERNOTE: Before checking idle speed, the engine should be allowed to warm up After the engine speed is stabilized, check andor adjust the idle speed
1Start the outboard motor2Attach the engine tachometer to the spark plug high-tension cord