Mercury - Blue Plastic Drain Plug For MerCruiser Blocks, Manifolds & Pumps 806608K01. Overview. Routine maintenance shouldn't be a hassle. The Mercury Marine 806608K01 Blue Plastic Drain Plug makes draining water from your MerCruiser engine block, exhaust manifolds, seawater pumps, or drain ports simple and mess-free. Built from durable, corrosion-resistant plastic, it's designed to last through years of seasonal use. Its bright blue color makes it easy to spot during maintenance, and the includ