Mercury - Quicksilver Thermostat Housing Gasket Cooling System Seal Marine-Grade Composite 530451. Overview. Keeping your cooling system sealed tight is key to consistent engine temperatures and smooth performance. The Mercury Marine 530451 Quicksilver Thermostat Housing Gasket is built for V6 and V8 MerCruiser sterndrives and inboard engines made by General Motors, as well as similar engines used by OMC and Volvo Penta. Made from durable, heat-resistant composite material, this gasket ensures a