Yamaha - Gear 2 (21 Tooth) Lower Unit Gear Component 6CB-45571-00-00. Overview. This is one of those parts you don't think about-until the lower unit starts acting up. The Yamaha Gear 2 (21 Tooth) sits deep inside the gearcase, handling load transfer and helping keep everything turning smoothly under power. When it wears, you'll hear it before you see it-grinding, slipping, or just not feeling right under throttle. Swapping it out restores that solid, confident feel when you drop it into gear and get moving.. Key Features. • 21-Tooth Gear Design - Engineered to maintain proper gear ratio and smooth power transfer.. • Precision Machined Teeth - Ensures clean engagement and reduces internal wear.. • OEM Fit Accuracy - Matches Yamaha factory specs for proper alignment and performance.. • High Strength Material - Built to handle torque, shock loads, and harsh marine use.. Engine & Boat Compatibility. Verify compatibility with your specific Yamaha outboard model and part number before insta