{"product_id":"sierra-18-3551-marine-engine-thermostat-160-degrees-f-replaces-oem-2463441-fits-318-360-cid-engines","title":"Sierra 18-3551 Marine Thermostat for 140 HP 6-Cylinder Engines, Replaces 1538930 1725960","description":"\u003cp\u003eThe Sierra 18-3551 is a marine engine thermostat built as a direct replacement for 140 HP 6-cylinder marine engines. It regulates coolant flow through the engine block, opening at 142 degrees F to keep raw water cooled engines running at the correct operating temperature and preventing the overheating or over-cooling that can damage cylinder heads, gaskets, and exhaust components over time. The thermostat is constructed of a metal and plastic composite housing designed to hold up under continuous marine duty in a raw water cooling system.\u003c\/p\u003e\u003cp\u003eThis part directly replaces OEM numbers 1538930 and 1725960, making it a straightforward swap for boat owners maintaining or rebuilding a 140 HP 6-cylinder marine powerplant. At just 0.12 pounds, it is a compact, easy-to-handle component that fits into the factory thermostat housing without modification. Sierra manufactures the 18-3551 to match the fit, form, and function of the original equipment thermostat it replaces, so cooling system performance and engine temperature regulation remain consistent with the factory setup.\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 18-3551\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Type:\u003c\/strong\u003e Marine Thermostat\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.12 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTemperature Rating:\u003c\/strong\u003e 142 degrees F\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Metal\/Plastic Composite\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 030999316004\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEngine Fitment:\u003c\/strong\u003e 140 HP 6-Cylinder engines\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM Cross Reference:\u003c\/strong\u003e 1538930, 1725960\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e140 HP 6-Cylinder marine engines\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e1538930\u003c\/li\u003e\n\u003cli\u003e1725960\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat engines does the Sierra 18-3551 thermostat fit?\u003c\/strong\u003e The Sierra 18-3551 is designed for 140 HP 6-cylinder marine engines.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat temperature does the 18-3551 thermostat open at?\u003c\/strong\u003e It is rated to open at 142 degrees F, which is the standard operating temperature for the raw water cooled marine engines it services.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat OEM part numbers does the Sierra 18-3551 replace?\u003c\/strong\u003e This thermostat replaces OEM numbers 1538930 and 1725960.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the Sierra 18-3551 thermostat weigh?\u003c\/strong\u003e The Sierra 18-3551 weighs 0.12 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat material is the 18-3551 thermostat made of?\u003c\/strong\u003e Sierra 18-3551 uses a metal and plastic composite construction for the housing and internal components.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-3551 a genuine Sierra part or generic aftermarket?\u003c\/strong\u003e The 18-3551 is manufactured by Sierra as a direct aftermarket replacement engineered to match the fit and function of the original 1538930 and 1725960 thermostats.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is included when ordering the Sierra 18-3551?\u003c\/strong\u003e Ordering the Sierra 18-3551 includes one thermostat unit.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill the 18-3551 work in a closed cooling system?\u003c\/strong\u003e The Sierra 18-3551 is intended for engines using raw water cooling; confirm your engine's cooling configuration before installing.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the Sierra 18-3551 include a gasket or housing?\u003c\/strong\u003e The Sierra 18-3551 is the thermostat itself; the thermostat housing and gasket are separate components.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow do I know if I need the 18-3551 versus a different Sierra thermostat?\u003c\/strong\u003e Confirm your engine is a 140 HP 6-cylinder model and cross-check your original thermostat against OEM numbers 1538930 or 1725960 before ordering the 18-3551.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988153053403,"sku":"SIE-18-3551","price":16.71,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/SIE-18-3551_lg__51506.1558126605.500.750.jpg?v=1785188116","url":"https:\/\/www.goodvibesmarina.com\/products\/sierra-18-3551-marine-engine-thermostat-160-degrees-f-replaces-oem-2463441-fits-318-360-cid-engines","provider":"Good Vibes Marina","version":"1.0","type":"link"}