Yamaha - Gear Unit Assembly Lower Unit & Propulsion System 6EG-E3102-00-00. Overview. When a gear unit starts giving trouble, it's not something you can ignore-noise, slipping, or loss of power shows up fast. I've worked on plenty of Yamaha setups where swapping in a complete unit saved time and avoided bigger issues down the road. This is the part doing all the work below the waterline, taking load every time you throttle up. When it's solid, the boat runs smooth, quiet, and dependable.. Key Fe