Yamaha - Lower Unit Assembly Drivetrain System 6E5-45300-28-8D. Overview. When a lower unit starts acting up, it's usually not something you want to piece together part by part. I've seen guys try to chase down individual issues, only to end up replacing everything anyway. A complete lower unit assembly like this just takes all the uncertainty out of it. Bolt it on, set it up right, and you're back to smooth, reliable running on the water.. Key Features. Complete Bolt-On Assembly - Comes fully assembled to simplify installation and reduce downtime.. Smooth Power Transfer - Delivers consistent performance from the driveshaft to the prop.. Heavy-Duty Construction - Built to handle torque, load, and real-world marine conditions.. Corrosion-Resistant Design - Helps protect against saltwater exposure and long-term wear.. Engine & Boat Compatibility. Designed for Yamaha 2-stroke outboard engines with standard lower unit configurations. Commonly used on mid-range horsepower motors found on fi