Yamaha - Lower Unit Assembly Gearcase Component 6EG-G5300-10-8D. Overview. The Yamaha Lower Unit Assembly 6EG-G5300-10-8D is what turns your small engine's power into real movement on the water. On a 2.5 horsepower, everything needs to be tight and efficient, and when the lower unit starts to wear, you'll feel it right away. Whether it's noise, rough rotation, or just not pushing like it should, this is usually where the issue lives. Swapping in a solid assembly like this gets everything back to smooth, reliable operation.. Key Features. • Efficient Power Transfer - Delivers engine output to the propeller for smooth and 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 handle freshwater and saltwater use.. Engine & Boat Compatibility. • F2.5 2015-2018. FAQs.