New & Remanufactured Mercury & Mariner 3 & 4 Cylinder Outboard Gearcases

Explore OBParts’ selection of Mercury & Mariner three & four-cylinder outboard gearcases, including both new and remanufactured OBR and SEI lower units. Available for a range of models—from 50/55/60 HP Bigfoot units (1991–2008) to 75–125 HP DFI/Optimax units (2004–2018)—these gearcases are designed to fit multiple configurations (3-jaw and 6-jaw) and offer direct replacements from trusted brands like OBR and SEI. Whether you need a cost-effective remanufactured option or a brand‑new component, OBParts simplifies sourcing quality parts for Mercury & Mariner outboards.