Yamaha - Gear 1 (28 Tooth) Lower Unit Gear Train 6EH-45560-00-00. Overview. When you're dealing with lower unit gears, even small wear shows up fast on the water. I've opened up gearcases where one worn gear turned into noise, vibration, and eventually bigger damage. This gear is part of that chain that keeps power moving clean from the engine to the prop. When it's in good shape, everything runs quiet and smooth like you expect from a Yamaha.. Key Features. • 28 Tooth Gear Design - Precisely cut teeth ensure proper engagement within the gear train.• Smooth Power Transfer - Helps deliver consistent torque through the lower unit.• Hardened Metal Construction - Built to handle load, friction, and long-term marine use.• Reliable Gear Engagement - Supports clean meshing to reduce wear on surrounding components.• Exact Yamaha Fitment - Designed to match factory specifications for proper alignment and function.. Engine & Boat Compatibility. Designed for Yamaha outboard lower units utilizing