2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 41Get this manual
PERIODIC MAINTENANCE BATTERY
BATTERY
I INSPECT EVERY 50 HOURS (3 MONTHS)
AWARNING
Never expose battery to open flame or electric spark as batteries generate gas, which is flammable and explosive Battery acid is poisonous and corrosiveAvoid contact with eyes, skin, clothing, and painted surfacesIf battery acid comes in contact with any of these, flush immediately with large amounts of waterIf acid contacts the eyes or skin, get immediate medical attention Batteries should always be kept out of reach of children When checking or servicing the battery, disconnect the negative (black) cableBe careful not to cause short circuit by allowing metal objects to contact the battery posts and the motor at the same time Wear approved eye protectionRecommended battery: 12 360CCA (465MCA) with 90 minute reserveCONNECTING BATTERY