Yamaha - Lower Unit Assembly VF90 Complete Drivetrain Assembly 6HK-45300-10-NA. Overview. The Yamaha Lower Unit Assembly VF90 6HK-45300-10-NA is what puts your engine's power to work where it matters-below the waterline. When a lower unit starts acting up, you'll feel it fast with vibration, noise, or loss of performance at the prop. Instead of chasing internal issues, swapping the full unit is usually the most reliable way to get things back on track. It gives you a solid, ready-to-run setup so you can focus on the water, not what's happening underneath.. Key Features. • Complete Drivetrain Assembly - Replaces internal gears and components in one unit for dependable performance.. • OEM Fit Precision - Built to Yamaha specifications for proper alignment and straightforward installation.. • Smooth Power Transfer - Supports consistent thrust and reliable operation under load.. • Corrosion-Resistant Construction - Designed to handle harsh marine environments and long-term use.. Engine & B