Yamaha 6AU-45300-10-4D Lower Unit Assembly

The Yamaha 6AU-45300-10-4D lower unit assembly is a precision-engineered gearcase designed for Yamaha 4-stroke F8 and F9.9 outboard motors. This long shaft configuration integrates the gearcase housing, driveshaft, propeller shaft, forward and reverse gears, and water pump housing into a single unit. Manufactured to OEM specifications, it ensures correct gear ratio, spline engagement, and sealing for reliable power transmission in marine environments. The aluminum alloy construction provides corrosion resistance and structural integrity under operational loads. This assembly replaces multiple superseded part numbers across the 6AU-45300 series. Compatible with Yamaha F9.9J and F9.9F engine models. Direct interchange for OEM part numbers 6AU-45300-00-4D, 6AU-45300-12-8D, and aftermarket reference 68T-45300-00-4D. Installation requires standard marine lower unit tools and torque specifications per Yamaha service manual.