The Boat Waterlock & Silencer is designed to prevent exhaust water backflow and reduce noise produced by the exhaust to minimum. This heavy-duty waterlock and muffler is recommended for most sailboats and motor yachts with gasoline or diesel engines and water cooled generator sets up to 30HP. Compact design facilitates durable installation with 4 screws x 8mm. It is constructed of high density rotational molded polyethylene which is impervious to corrosion or deterioration from salt water or exhaust from gas. Also, it is resistant to all temperatures normally experienced in water-cooled (wet-type) exhaust systems. With a 25.4 mm drain outlet for system cleaning.