Yamaha - Gear Set Lower Unit Gear Set 6CF-45550-00-00. Overview. When you're rebuilding a Yamaha lower unit, the gear set is where everything either comes together or falls apart. If one gear is worn, it usually affects the whole system, and you'll feel it in noise, shifting, and overall performance. I've worked on units where replacing the full gear set brought everything back to smooth, quiet operation. When it's right, the drivetrain runs clean and you can trust it under load.. Key Features. • Complete Gear Set Configuration - Includes matched gears designed to work together for smooth operation.• Precision-Cut Gear Teeth - Ensures proper meshing to reduce noise and vibration.• High-Strength Construction - Built to handle torque and continuous load in marine conditions.• Consistent Power Transfer - Supports efficient movement of power through the lower unit.• Factory-Spec Fitment - Designed to meet Yamaha tolerances for proper alignment and performance.. Engine & Boat Compatibility.