Yamaha - Lower Unit Assembly Gearcase Component 6P3-45300-41-8D. Overview. On these bigger Yamaha setups, the lower unit takes a beating, especially if you're running hard or in rough water. I've replaced enough of them to know that a complete assembly like this saves time and headaches compared to piecing things together. Everything lines up the way it should, and you get back that smooth, solid feel at the helm. It's the kind of upgrade that brings confidence back to every run.. Key Features. • Complete Gearcase Assembly - Provides a full replacement with matched internal components.• Smooth Power Transfer - Delivers consistent output from engine to propeller.• OEM Engineered Fit - Built to Yamaha specifications for proper alignment and performance.• Heavy-Duty Marine Build - Designed to handle high horsepower and demanding conditions.. Engine & Boat Compatibility. Designed for Yamaha outboard engines, including high-performance models like the LF series. Commonly used across a range