Yamaha - Lower Unit Assembly Gearcase Component 6EK-45300-11-8D. Overview. The Yamaha Lower Unit Assembly 6EK-45300-11-8D is what keeps your engine's power turning into real push on the water. When a lower unit starts going bad, you'll feel it right away-noise, vibration, or loss of performance. This assembly handles the gears, driveshaft, and prop output, so everything depends on it being solid and aligned. If you're replacing a worn or damaged unit, this is the kind of part that brings your motor back to running like it should.. Key Features. • Efficient Power Transfer - Delivers engine power smoothly to the propeller for reliable performance.. • OEM Fit Precision - Built to Yamaha specifications for proper alignment and straightforward installation.. • Complete Gearcase Assembly - Pre-assembled unit for easier replacement and dependable operation.. • Corrosion-Resistant Construction - Designed to withstand harsh saltwater and freshwater environments.. Engine & Boat Compatibility. •