Yamaha - Lower Unit Assembly Drivetrain System 6E5-45300-17-8D. Overview. When a bigger Yamaha like a 115 or 130 starts having lower unit issues, you feel it right away-noise, rough shifting, or just not running as smooth as it should. At that point, rebuilding can turn into a long process with mixed results. I've found that going with a complete lower unit assembly like this saves time and gets you back on the water with confidence. It's the kind of fix that brings everything back to smooth, dependable operation in one shot.. Key Features. Complete Bolt-On Assembly - Comes ready for installation to minimize downtime and simplify replacement.. High Load Gear Performance - Designed to handle the torque and demand of mid-range outboards.. Corrosion-Resistant Build - Built to stand up to saltwater use and harsh marine conditions.. Factory-Matched Fitment - Aligns properly with Yamaha drivetrains for smooth operation and reliable shifting.. Engine & Boat Compatibility. Designed for Yamaha