Yamaha - Gear 1 Lower Unit Gear Component 6J9-45560-03-00. Overview. The Yamaha Gear 1 6J9-45560-03-00 is one of those internal parts you don't see, but you definitely feel when something's off. When gears start wearing down, you'll notice it in rough shifting, noise, or even power loss under load. This gear plays a key role in transferring power through the lower unit, so it needs to stay solid and properly meshed. If you're rebuilding or repairing a lower unit, this is one of those parts you don't want to cut corners on.. Key Features. • Reliable Power Transfer - Helps move engine power through the lower unit for consistent performance.. • OEM Fit Precision - Designed to match Yamaha gear specs for proper meshing and operation.. • Smooth Gear Operation - Supports clean engagement and reduces internal resistance.. • Heavy-Duty Construction - Built to handle torque, load, and continuous marine use.. Compatibility. Compatible with select Yamaha outboard engines using this lower unit gea