Mercury - Quicksilver Thermostat Gasket Cooling System Seal Marine-Grade Composite 33179Q02. Overview. Your MerCruiser's cooling system depends on a perfect seal to perform at its best. The Mercury Marine 33179Q02 Quicksilver Thermostat Gasket is designed for MerCruiser V6 and V8 engines with a flat thermostat cover plate, ensuring a tight fit that prevents leaks and maintains consistent cooling temperatures. Made from durable, marine-grade composite material, this gasket stands up to heat, vibr