Yamaha Lower Unit Gasket - 6GR-W0001-21-00. Ensure a Tight, Leak-Free Seal for Your Yamaha Outboard's Lower Unit. The Yamaha - Lower unit gasket - 6GR-W0001-21-00 is a genuine OEM replacement designed to maintain a reliable seal between the gearcase and midsection of your Yamaha outboard engine. Crafted from marine-grade materials, this gasket is engineered to prevent water intrusion and oil leaks-protecting internal components and preserving overall performance.. When servicing or replacing you