Yamaha - Lower Unit Assembly Complete Lower Unit System 69M-G5300-10-4D. Overview. When your lower unit is running right, everything just feels smooth-clean shifts, solid hookup, and no surprises when you throttle up. But once it starts going bad, you'll hear it and feel it fast, especially under load. This is the kind of replacement you go with when you want to stop chasing internal issues and just get back to reliable performance. Built for real-world use, it's meant to handle long runs, heavy loads, and whatever the water throws at you.. Key Features. Complete Lower Unit Assembly - Provides a full replacement without the need for internal rebuild work.. Smooth Power Transfer - Delivers consistent torque from the engine to the propeller.. Reliable Shift Engagement - Designed for clean forward and reverse operation under load.. Factory-Aligned Components - Built to Yamaha specifications for proper fit and dependable performance.. Engine & Boat Compatibility. Designed for Yamaha outboa