Yamaha Pinion - 6T5-45551-00-00. OEM Yamaha Pinion Gear for Smooth, Precise Gearcase Function. The Yamaha - Pinion - 6T5-45551-00-00 is a genuine factory-engineered gear designed to deliver accurate and consistent power transfer within your Yamaha outboard's lower unit. As a foundational part of the gearcase assembly, this pinion engages directly with the forward and reverse gears, ensuring responsive acceleration and clean shifting under load.. Manufactured to Yamaha's exact specifications, thi