Mercury - Quicksilver Exhaust Water Shutter Kit For Select MerCruiser Sterndrive Engines 807166A2. Overview. When your boat's sitting still or idling in rough water, the last thing you want is seawater creeping back into your engine. The Mercury Marine 807166A2 Quicksilver Exhaust Water Shutter Kit stops that from happening. Designed for MerCruiser sterndrives with Y-pipes measuring 2.98 inches at the cross pin, this kit acts as a one-way valve - letting exhaust exit freely while blocking water