Yamaha - Gear 2 (21T) Lower Unit Gear 6CE-45571-00-00. Overview. Inside a Yamaha lower unit, every gear has to work together perfectly, and this one plays a key role in keeping things running smooth under load. When a gear starts to wear, you'll feel it in noise, rough engagement, or even slipping. I've replaced worn gears like this and seen the whole system quiet down and run cleaner. When it's right, shifting and power delivery feel solid and dependable.. Key Features. • 21-Tooth Gear Design - Precisely cut teeth ensure smooth engagement and consistent rotation.• High-Strength Construction - Built to handle torque and repeated use without early wear.• Smooth Gear Interaction - Helps reduce vibration and noise during operation.• Precision Fit Engineering - Matches Yamaha specifications for proper alignment and function.• Wear-Resistant Surface - Designed to withstand internal friction and marine conditions.. Engine & Boat Compatibility. Designed for Yamaha outboard lower units requiri