Yamaha - Lower Unit Assembly F250 Complete Drivetrain Assembly 6P2-45300-42-8D. Overview. The Yamaha Lower Unit Assembly F250 6P2-45300-42-8D is what takes all that horsepower and actually puts it to work in the water. When a lower unit starts going bad on a motor like the F250, you'll feel it right away-vibration, noise, or a drop in performance when you're on plane. Instead of chasing internal gear issues, replacing the full assembly is usually the most reliable fix. It gives you a solid, ready-to-run setup so you can stay focused on the water.. 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 efficient thrust and consistent operation under heavy load.. • Heavy-Duty Construction - Designed to handle high horsepower, torque, and harsh marine environments.. Engine & B