ARCO Marine Mercury Outboard Starter - 9 ToothMercury Outboard Starter 9 Tooth The outboard starter will fit Mercury Mariner 40 HP, 50 HP, 60 HP 4 cyl, 4 Stroke, and 9 tooth drive gear. ARCO advises using a fully charged battery A weak battery can damage the starter and starter solenoid. And to also clean all connections A corroded connection creates resistance, lowering the amperage required for an efficient starting circuit. Features: Dynamically tested and packaged for out of the box