Yamaha - Lower Unit Assembly Gearcase Component 6EG-G5300-00-8D. Overview. The Yamaha Lower Unit Assembly 6EG-G5300-00-8D is what keeps your small outboard putting power where it matters-into the water. On F2.5 engines, you'll notice right away if the lower unit starts wearing out, whether it's noise, rough rotation, or loss of push. This assembly handles everything from gear transfer to prop rotation, so it has to stay solid and aligned. If your motor isn't performing like it should, replacing the lower unit is often the cleanest fix.. Key Features. • Efficient Power Transfer - Delivers engine output smoothly to the propeller for consistent performance.. • OEM Fit Precision - Built to Yamaha specifications for proper alignment and easy installation.. • Complete Gearcase Assembly - Pre-assembled unit for straightforward replacement and dependable operation.. • Corrosion-Resistant Construction - Designed to withstand saltwater and freshwater environments.. Engine & Boat Compatibility. •