Sierra 18-6421 Outboard StarterSierra marine starters are designed for spark/ignition protection to prevent ignition of fuel vapor contained within the bilge of a boat. These units are sealed to prevent water intrusion and corrosion and are tested for Coast Guard and CE compliance. Sierra replacement outboard starter for use on Yamaha Outboards. 11 Tooth Drive Gear; Interchangeable with: Arco; 3423; Hitachi; S108-87A; Mallory; 9-15050; Yamaha Outboard; 6J4-81800-01-00; 6F5-81800-11-00; 6F5-81800-10-00; 6J4-81800-00-00;