Stern drive exhaust water shutter 807166A1 is for use on MerCruiser stern drives to keep following seas/water from washing back into the exhaust system and into the engine when engine is not running or at low RPM. Shutter is 2.48" diameter at cross pin (hinge pin) See your owner's manual or service manual for specific applications and replacement instructions. The Quicksilver brand is the leader in delivering uncompromising engine oils, parts and accessories to the marine industry for over 65 years. Quicksilver is the premier supplier of Mercury Marine original Equipment replacement engine parts, oils, and accessories, but also works to serve all original Equipment brands in the marine and powersports industries. It has earned a loyal following by providing the highest quality products that are tested through some of the most rigorous environments and testing procedures. No aftermarket company comes close to the level of research and design as Quicksilver; buying Quicksilver is buying performance, protection and peace of mind.