Yamaha - Gear Lower Unit Gear Train 6EM-45560-00-00. Overview. When you're inside a lower unit, gears are where everything either works right-or doesn't. I've seen worn gears turn a smooth-running motor into something noisy and unpredictable in no time. This is one of those parts that takes constant load every time you're on the throttle. When it's in good shape, power transfers clean and quiet, just like you expect from a Yamaha.. Key Features. • Precision-Cut Gear Teeth - Ensures proper meshing with other gears for smooth operation.• Consistent Power Transfer - Helps deliver steady torque through the lower unit.• Hardened Metal Construction - Built to withstand load, friction, and long-term use.• Reduced Gear Wear - Designed for clean engagement to minimize internal stress.• Exact Yamaha Fitment - Matches factory specifications for proper alignment and function.. Engine & Boat Compatibility. Designed for Yamaha outboard lower units utilizing internal gear train systems. Commonly used