Yamaha - Lower Unit Assembly Complete Lower Unit System 69W-45300-01-8D. Overview. When a lower unit is in good shape, you feel it right away-smooth shifting, solid bite, and no extra noise when you put it in gear. But once things start wearing out, it shows up fast with vibration or rough engagement. This is the kind of replacement you go with when you want everything back to running clean without digging into internal repairs. It's built for everyday use, whether you're cruising, working, or putting in long hours on the water.. Key Features. Complete Lower Unit Assembly - Provides a full replacement solution without internal teardown or rebuild.. Smooth Power Transfer - Delivers consistent torque from engine to propeller for steady performance.. Clean Shift Operation - Designed for reliable forward and reverse engagement under load.. OEM Fit and Alignment - Built to Yamaha specifications for proper installation and dependable use.. Engine & Boat Compatibility. Designed for Yamaha out