{"product_id":"sierra-18-0539-exhaust-leg-rubber-seal-gasket-for-mercury-outboards-replaces-mercury-37721-37721001-glm-85630","title":"Sierra 18-0539 Rubber Seal Gasket - Replaces Mercury 37721","description":"\u003cp\u003eThe Sierra 18-0539 Rubber Seal Gasket is a rubber exhaust leg seal used in Mercury outboard cooling systems. It is designed as a direct replacement for the original equipment seal, restoring a tight, leak-free connection where the exhaust leg meets the powerhead cooling passages. A worn or hardened rubber seal in this location can allow water or exhaust gases to escape past the joint, so replacing it with a properly sized gasket like the 18-0539 helps maintain correct sealing pressure and cooling system integrity.\u003c\/p\u003e\u003cp\u003eMade of rubber, this seal is compact and precisely sized to fit its intended mounting location, with dimensions of 0.39 x 0.39 x 0.39 inches and a weight of 0.07 pounds. It is built to meet or exceed the quality of the original equipment part it replaces, making it a reliable choice for routine maintenance or repair of the exhaust cooling seal. This is a small, low-cost component, but correct fitment matters since it is engineered as a like-for-like replacement for Mercury 37721.\u003c\/p\u003e\u003ch3\u003eSpecifications\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBrand:\u003c\/strong\u003e Sierra\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer Part Number:\u003c\/strong\u003e 18-0539\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Name:\u003c\/strong\u003e Rubber Seal Gasket\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Rubber\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.07 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Dimensions:\u003c\/strong\u003e 0.39 x 0.39 x 0.39 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 030999874474\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\u003cli\u003eMercury 37721\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat is the Sierra 18-0539 used for?\u003c\/strong\u003e The Sierra 18-0539 is a rubber seal gasket used in the exhaust leg area of Mercury outboard cooling systems, sealing the joint to prevent water or exhaust leaks.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-0539 a direct replacement for Mercury 37721?\u003c\/strong\u003e Yes, the 18-0539 is manufactured as a direct replacement for Mercury part 37721.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat material is the 18-0539 seal made from?\u003c\/strong\u003e It is made of rubber, which allows it to compress and form a tight seal against mating surfaces.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the Sierra 18-0539 gasket weigh?\u003c\/strong\u003e This gasket weighs 0.07 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat are the dimensions of the 18-0539 rubber seal?\u003c\/strong\u003e The seal measures 0.39 x 0.39 x 0.39 inches.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the Sierra 18-0539 meet OEM quality standards?\u003c\/strong\u003e Sierra manufactures the 18-0539 to meet or exceed the quality of the original equipment Mercury 37721 seal it replaces.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the UPC for the Sierra 18-0539 gasket?\u003c\/strong\u003e The UPC for the Sierra 18-0539 Rubber Seal Gasket is 030999874474.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the 18-0539 only for Mercury outboards?\u003c\/strong\u003e The 18-0539 is designed to replace the Mercury 37721 seal used in Mercury outboard cooling systems.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat comes in the package with the 18-0539?\u003c\/strong\u003e The Sierra 18-0539 is sold as a single rubber seal gasket.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy would I need to replace this rubber seal?\u003c\/strong\u003e Over time the rubber in an exhaust leg seal like the 18-0539 can harden or crack, allowing leaks; replacing it with a new Sierra 18-0539 restores a proper seal.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan the Sierra 18-0539 be reused after removal?\u003c\/strong\u003e No, once a rubber seal gasket like the 18-0539 is compressed and removed it typically loses its sealing ability and should be replaced with a new one.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988077064411,"sku":"SIE-18-0539","price":8.35,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/SIE-18-0539_lg__42314.1558119442.500.750.jpg?v=1785189148","url":"https:\/\/www.goodvibesmarina.com\/products\/sierra-18-0539-exhaust-leg-rubber-seal-gasket-for-mercury-outboards-replaces-mercury-37721-37721001-glm-85630","provider":"Good Vibes Marina","version":"1.0","type":"link"}