Yamaha - Gear 2 Lower Unit Gearcase Component 6H3-45571-00-00. Overview. When a lower unit starts making noise or slipping under load, gears are usually where the problem shows up. I've opened up gearcases where this gear was worn just enough to cause rough engagement or inconsistent performance. It's not something you want to ignore, because it only gets worse with use. Replacing it the right way brings the drivetrain back to smooth, reliable operation.. Key Features. Precision Gear Engagement - Transfers power within the gearcase for smooth and consistent operation.. Hardened Gear Construction - Built to handle torque and resist wear under continuous use.. OEM-Spec Machining - Designed to Yamaha tolerances for proper gear mesh and alignment.. Reliable Power Transfer - Supports steady propulsion without slipping or abnormal noise.. Critical Drivetrain Component - Essential for proper lower unit function and long-term durability.. Engine & Boat Compatibility. Designed for Yamaha outboa