Mercury - Quicksilver Blue Plastic Drain Plug Kit For MerCruiser Engines 806608Q01. Overview. When it's time to drain your cooling system or prep your boat for winter, the Mercury Marine 806608Q01 Quicksilver Blue Plastic Drain Plug Kit makes the job simple and mess-free. Designed for MerCruiser sterndrive and inboard engines, this plug fits your cylinder blocks, exhaust manifolds, seawater pumps, and hose drain ports perfectly. It's built from corrosion-resistant plastic that stands up to saltw