Yamaha - Lower Unit Assembly Outboard Drivetrain 6L2-45300-04-4D. Overview. When a lower unit starts giving trouble, you'll feel it right away-rough shifting, noise, or just not running as smooth as it should. This is the kind of replacement that brings everything back to life without overthinking it. It bolts up clean, runs quiet, and gives you that steady, predictable performance you want on the water. Whether you're maintaining your setup or fixing a problem, this is a solid way to get back to reliable operation.. Key Features. Smooth Power Transfer - Delivers consistent engine output to the propeller with minimal vibration.. Corrosion-Resistant Construction - Built to handle saltwater and harsh marine conditions.. Factory-Spec Fitment - Designed for proper alignment and seamless installation on Yamaha outboards.. Durable Internal Gearing - Supports long-term performance under regular use and load.. Complete Assembly Unit - Pre-assembled design reduces downtime and simplifies replac