{"product_id":"sierra-18-3668-marine-thermostat-kit-160-degree-replaces-807252t4-fits-mercruiser-engines","title":"Sierra 18-3668 Thermostat Kit for MerCruiser 5.0LX and 898 305 cid V-8 Engines","description":"\u003cp\u003eThe Sierra 18-3668 Thermostat Kit is a marine engine thermostat built for MerCruiser stern drive and inboard applications, replacing the factory thermostat as part of routine cooling system maintenance or repair. It is a Design II configuration with a check ball, which allows trapped air to bleed from the cooling system as the engine warms up, helping the engine reach and hold proper operating temperature. The housing and internals are finished in white and operate automatically using a mechanical wax-pellet style control, requiring no electrical connection or manual adjustment.\u003c\/p\u003e\u003cp\u003eThis thermostat kit is built to marine specifications, since automotive thermostats are not designed to handle the raw water or closed cooling demands of a boat engine. Sierra manufactures marine parts to meet or exceed the performance of the original equipment they replace, making the 18-3668 a straightforward drop-in option for the engine applications it covers. Each kit is packaged as a single unit count, ready to install during a cooling system service or when replacing a thermostat that is stuck open, stuck closed, or no longer regulating temperature correctly.\u003c\/p\u003e\u003cp\u003eThe 18-3668 is specified for MerCruiser 5.0LX 305 cid V-8 engines built from 1988 to 1995, and for MerCruiser 898 305 cid V-8 engines built from 1983 to 1984. Confirm your engine model and production years against these ranges before ordering to be sure you get the correct thermostat design for your application.\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 18-3668\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Type:\u003c\/strong\u003e Thermostat Kit\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDesign Type:\u003c\/strong\u003e Design II, with check ball\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eColor:\u003c\/strong\u003e White\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTemperature Control Type:\u003c\/strong\u003e Automatic\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePower Source:\u003c\/strong\u003e Mechanical\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.17 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 030999316318\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnit Count:\u003c\/strong\u003e 1 count\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eMerCruiser 5.0LX 305 cid V-8, 1988-1995\u003c\/li\u003e\n\u003cli\u003eMerCruiser 898 305 cid V-8, 1983-1984\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat engines is the Sierra 18-3668 thermostat kit designed for?\u003c\/strong\u003e The 18-3668 is specified for MerCruiser 5.0LX 305 cid V-8 engines built from 1988 to 1995, and for MerCruiser 898 305 cid V-8 engines built from 1983 to 1984.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the 18-3668 have a check ball?\u003c\/strong\u003e Yes, the Sierra 18-3668 is a Design II thermostat that includes a check ball, which helps bleed trapped air from the cooling system as the engine reaches operating temperature.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the 18-3668 thermostat kit weigh?\u003c\/strong\u003e The Sierra 18-3668 Thermostat Kit weighs 0.17 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat color is the Sierra 18-3668 thermostat?\u003c\/strong\u003e This thermostat kit is finished in white.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the 18-3668 an automatic or manually adjusted thermostat?\u003c\/strong\u003e It operates automatically using a mechanical, wax-pellet style control, so no manual adjustment or electrical connection is needed.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use an automotive thermostat instead of the 18-3668 on my MerCruiser engine?\u003c\/strong\u003e No, the 18-3668 is built to marine specifications for MerCruiser 5.0LX and 898 305 cid V-8 engines, since automotive thermostats are not designed for a boat's raw water or closed cooling system demands.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is included with the Sierra 18-3668 kit?\u003c\/strong\u003e The Sierra 18-3668 Thermostat Kit ships as a single unit count containing the thermostat for the listed MerCruiser applications.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhen should I replace the thermostat on my MerCruiser 305 V-8?\u003c\/strong\u003e A thermostat like the Sierra 18-3668 should be replaced when it sticks open or closed, causing the MerCruiser engine to run too cool or overheat, or as part of scheduled cooling system maintenance.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill the 18-3668 fit a MerCruiser 898 built in 1985?\u003c\/strong\u003e The Sierra 18-3668 is specified for the MerCruiser 898 305 cid V-8 for the 1983 to 1984 model years, so confirm your engine's build year falls in that range before ordering.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-3668 a genuine Sierra part?\u003c\/strong\u003e Yes, 18-3668 is Sierra's own manufacturer part number for this thermostat kit, not a generic or third-party substitute.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988157247707,"sku":"SIE-18-3668","price":37.09,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/SIE-18-3668_lg__67967.1558127699.500.750.jpg?v=1785188367","url":"https:\/\/www.goodvibesmarina.com\/products\/sierra-18-3668-marine-thermostat-kit-160-degree-replaces-807252t4-fits-mercruiser-engines","provider":"Good Vibes Marina","version":"1.0","type":"link"}