Yamaha - Gear 1 (21 Tooth) Lower Unit Gear Component 6CB-45561-00-00. Overview. When you're dealing with lower unit issues, this is one of the gears that can make or break how the motor feels under load. Gear 1 handles a big part of the power transfer, and when it starts to wear, you'll hear it and feel it right away. I've seen these cause everything from rough shifting to full-on slipping under throttle. Getting a fresh, properly machined gear back in place brings everything back to that solid, tight Yamaha feel.. Key Features. • 21-Tooth Gear Design - Maintains proper gear ratio for smooth and efficient power transfer.. • Precision Cut Teeth - Ensures clean engagement and reduces internal drivetrain wear.. • OEM Fit Accuracy - Matches Yamaha factory specifications for proper alignment and function.. • High Strength Construction - Built to handle torque, load, and harsh marine conditions.. Engine & Boat Compatibility. Verify compatibility with your specific Yamaha outboard model and p