An added line of defense against exhaust backflow. Many exhaust installations include shutters to prevent water from traveling back up the exhaust and into riser and manifold. These water shutters are exposed to endless heat cycling and saltwater abuse that can speed up the corrosion process and cause failure; routine inspection and replacement is advised. Sierra has engineered these water shutters to match the OEM shutters on many MerCruiser installations and protect water from traveling back into the engine from the exhaust. Key Features Engineered to meet or exceed manufacturer specifications Sold in pairs (single connector and shutter p/n 18-2732) Protects sensitive engine components from being damaged by water traveling back through exhaust systemFits all MerCruiser #1 drives Backed by SeaStar Solutions Limited Two-Year Warranty The Sierra Engine Parts Selector In addition to water shutters, we offer a wide variety of other engine parts manufactured by Sierra. To see if we have the part you need, see ourEngine Parts Selector, where you can search by engine make, serial number and model or year of manufacture.ApplicationOEM Part NumberGLM89170Mallory9-42802MerCruiser Sterndrive807166A3, 14348A1, 14348, 14348A2