2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 29Get this manual
PERIODIC MAINTENANCE GEAR OIL
GEAR OIL
CHANGE INITIALLY AFTER 10 HOURS (1 MONTH) AND EVERY 100 HOURS (6 MONTHS)1Place outboard motor upright on level surface2Place an oil pan below it, then drain oil by removing the oil drain plug and the oil level plug3Fill with recommended gear oil through oil drain hole until oil just starts to flow out from oil level holeIACAUTION I
Use 772269 metric thread adapterGear oil amount: 170 ml (5.76.0 US limpoz) Recommended oil: Ultra HPF Gearcase Lubricant (PIN 775601)