Yamaha - Gear 2 Lower Unit Drivetrain 6E5-45571-01-00. Overview. When you're dealing with lower unit performance, gears are right at the center of it all. This gear takes constant load every time you're on the throttle, and once it starts to wear, you'll feel it through noise or rough operation. I've seen setups where one worn gear ends up affecting the whole drivetrain. Replacing it helps bring everything back to smooth, reliable power transfer.. Key Features. Precision Gear Engagement - Ensures smooth meshing with mating gears for consistent operation.. Hardened Metal Construction - Built to withstand torque, load, and long-term drivetrain stress.. Reduced Vibration Operation - Helps maintain balanced rotation for smoother performance.. OEM Fitment Accuracy - Matches original specifications for proper alignment and dependable installation.. Engine & Boat Compatibility. Designed for Yamaha 2-stroke outboard engines with standard lower unit gearcases. Commonly used on mid-range horsepo