Mercury Lower Unit & Gearcase Guide
Finding the right replacement lower unit for a Mercury outboard takes more than matching horsepower. Gearcase fitment can vary based on the engine family, serial number, shaft length, gear ratio, rotation, and other application-specific details.
The terms lower unit and gearcase are often used when referring to the lower assembly of an outboard. Throughout this guide, you'll see both terms used while learning how Mercury gearcase fitment works and what information is needed to identify the correct replacement.
The Gregor's Marine Lower Unit & Gearcase Center is designed to help you understand your options, identify the information you'll need, and shop genuine Mercury and Quicksilver gearcase assemblies and components.