{"product_id":"sierra-18-3550-marine-thermostat-140f-for-mercruiser-2-5l-3-0l-120-140-165-stern-drive-replaces-mercury-59078-f85068","title":"Sierra 18-3550 140 Degree Thermostat, Replaces 2324347, MerCruiser 120\/140\/2.5L L4","description":"\u003cp\u003eThe Sierra 18-3550 is a 140 degree F thermostat built for MerCruiser stern drive engines, regulating coolant flow so the engine reaches and holds proper operating temperature. Consistent temperature control protects against overheating and against the fuel-fouling and premature wear that comes from an engine running too cold, making the thermostat one of the most important small parts in the cooling system. The 18-3550 features a white housing and is sized to fit directly into the thermostat housing of the applicable MerCruiser L4 engines.\u003c\/p\u003e\u003cp\u003eThis thermostat is designed for MerCruiser 120 and 140 model stern drives built around the 153 cid and 181 cid L4 engine blocks, as well as the 2.5L 153 cid L4 engine. It is a direct equivalent for a range of original Mercury\/MerCruiser thermostats used across these engine families over their production runs, letting owners replace a worn or stuck thermostat without having to track down the original factory part number.\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 18-3550\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTemperature Rating:\u003c\/strong\u003e 140 degrees F\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eColor:\u003c\/strong\u003e White\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFitment:\u003c\/strong\u003e MerCruiser 120, 140, and 2.5L stern drives with 153 cid or 181 cid L4 engines\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.08 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 030999315991\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM Cross Reference:\u003c\/strong\u003e 2324347, 3377340, B531853, B531854, C853255, 2508261, B450800\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eMerCruiser 120, 153 cid L4, 1968-1972\u003c\/li\u003e\n\u003cli\u003eMerCruiser 120, 153 cid L4, 1972-1986\u003c\/li\u003e\n\u003cli\u003eMerCruiser 2.5L, 153 cid L4, 1987-1989\u003c\/li\u003e\n\u003cli\u003eMerCruiser 140, 181 cid L4, 1968-1986\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e2324347\u003c\/li\u003e\n\u003cli\u003e3377340\u003c\/li\u003e\n\u003cli\u003eB531853\u003c\/li\u003e\n\u003cli\u003eB531854\u003c\/li\u003e\n\u003cli\u003eC853255\u003c\/li\u003e\n\u003cli\u003e2508261\u003c\/li\u003e\n\u003cli\u003eB450800\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat temperature rating is the Sierra 18-3550 thermostat?\u003c\/strong\u003e The Sierra 18-3550 is rated at 140 degrees F, which is the standard operating temperature setting for the MerCruiser engines it is designed for.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhich MerCruiser engines does the 18-3550 thermostat fit?\u003c\/strong\u003e It fits MerCruiser 120 and 140 model stern drives with 153 cid or 181 cid L4 engines, as well as the 2.5L 153 cid L4 engine, covering model years 1968 through 1989 across those variants.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the 18-3550 replace factory Mercury\/MerCruiser thermostats?\u003c\/strong\u003e Yes, the Sierra 18-3550 is a direct equivalent for the original equipment thermostats used on these engines, cross-referencing to OEM numbers 2324347, 3377340, B531853, B531854, C853255, 2508261, and B450800.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat color is the 18-3550 thermostat housing?\u003c\/strong\u003e The Sierra 18-3550 thermostat has a white housing.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the Sierra 18-3550 thermostat weigh?\u003c\/strong\u003e It weighs 0.08 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the 18-3550 the right part for a 140 six-cylinder MerCruiser engine?\u003c\/strong\u003e No. The 140 six-cylinder engine uses a different Sierra part number, 18-3551, so buyers with that engine should order 18-3551 rather than the 18-3550.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs there a thermostat housing kit that pairs with the 18-3550?\u003c\/strong\u003e Sierra offers a related complete thermostat housing kit under part number 18-3650 for engines where the original housing is no longer available; the 18-3550 is the thermostat itself, sold separately from that housing kit.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is included when ordering the Sierra 18-3550?\u003c\/strong\u003e The 18-3550 order includes the Sierra 140 degree thermostat unit for MerCruiser 120\/140\/2.5L L4 engines, identified by UPC 030999315991.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow do I know if I need the 18-3550 versus a different Sierra thermostat number?\u003c\/strong\u003e The 18-3550 is specific to the MerCruiser 120, 140, and 2.5L L4 engines listed in its fitment; other engine models, including the 140 six-cylinder, use different Sierra part numbers such as 18-3551, so matching your engine model and OEM cross-reference number is important before ordering.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-3550 a genuine or aftermarket thermostat?\u003c\/strong\u003e The 18-3550 is a Sierra-branded replacement thermostat manufactured to match the specifications of the original MerCruiser factory thermostats it cross-references, rather than a factory Mercury part.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988152987867,"sku":"SIE-18-3550","price":28.17,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/SIE-18-3550_lg__68975.1558126536.500.750.jpg?v=1785188884","url":"https:\/\/www.goodvibesmarina.com\/products\/sierra-18-3550-marine-thermostat-140f-for-mercruiser-2-5l-3-0l-120-140-165-stern-drive-replaces-mercury-59078-f85068","provider":"Good Vibes Marina","version":"1.0","type":"link"}