{"product_id":"sierra-thermostat-sie-18-43017-indmar","title":"Sierra Marine Thermostat 18-43017 – Indmar S985009 \/ MerCruiser 8.1L 496 MAG Cooling System","description":"\u003cp data-end=\"503\" data-start=\"298\"\u003eThe \u003cstrong data-end=\"332\" data-start=\"302\"\u003eSierra 18-43017 Thermostat\u003c\/strong\u003e is a precision 160° temperature control thermostat designed for high-horsepower GM-based marine engines, including Indmar, MerCruiser, and other big-block applications.\u003c\/p\u003e\n\u003cp data-end=\"690\" data-start=\"505\"\u003eThis thermostat regulates coolant flow to maintain optimal engine operating temperature, ensuring proper combustion efficiency, engine protection, and consistent performance under load.\u003c\/p\u003e\n\u003cp data-end=\"865\" data-start=\"692\"\u003eEngineered to meet or exceed OEM specifications, this unit is a direct replacement for Indmar S985009 and multiple MerCruiser thermostat applications used in 8.1L platforms.\u003c\/p\u003e\n\u003chr data-end=\"870\" data-start=\"867\"\u003e\n\u003ch2 data-end=\"891\" data-start=\"872\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"891\" data-start=\"875\"\u003eKey Features\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003cul data-end=\"1277\" data-start=\"892\"\u003e\n\u003cli data-end=\"997\" data-start=\"892\"\u003e160° thermostat for optimal marine engine operating temperature \u003cspan data-state=\"closed\" class=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"1087\" data-start=\"998\"\u003eDesigned for raw water cooled GM marine engines \u003cspan data-state=\"closed\" class=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"1143\" data-start=\"1088\"\u003eImproves engine efficiency and prevents overheating\u003c\/li\u003e\n\u003cli data-end=\"1190\" data-start=\"1144\"\u003eDirect OEM replacement fit and performance\u003c\/li\u003e\n\u003cli data-end=\"1240\" data-start=\"1191\"\u003eCorrosion-resistant marine-grade construction\u003c\/li\u003e\n\u003cli data-end=\"1277\" data-start=\"1241\"\u003eSierra limited lifetime warranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr data-end=\"1282\" data-start=\"1279\"\u003e\n\u003ch2 data-end=\"1311\" data-start=\"1284\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"1311\" data-start=\"1287\"\u003eEngine Compatibility\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003ch3 data-end=\"1354\" data-start=\"1313\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"1354\" data-start=\"1317\"\u003eMerCruiser (Big Block GM Engines)\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h3\u003e\n\u003cul data-end=\"1411\" data-start=\"1355\"\u003e\n\u003cli data-end=\"1373\" data-start=\"1355\"\u003e8.1L (496 MAG)\u003c\/li\u003e\n\u003cli data-end=\"1388\" data-start=\"1374\"\u003e496 MAG HO\u003c\/li\u003e\n\u003cli data-end=\"1411\" data-start=\"1389\"\u003e8.1L MIE \/ Horizon\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3 data-end=\"1442\" data-start=\"1413\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"1442\" data-start=\"1417\"\u003eIndmar Marine Engines\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h3\u003e\n\u003cul data-end=\"1566\" data-start=\"1443\"\u003e\n\u003cli data-end=\"1468\" data-start=\"1443\"\u003eGM-based 8.1L engines\u003c\/li\u003e\n\u003cli data-end=\"1566\" data-start=\"1469\"\u003eFord \u0026amp; GM raw water cooled applications (select models) \u003cspan data-state=\"closed\" class=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"1661\" data-start=\"1568\"\u003e➡️ Specifically designed for \u003cstrong data-end=\"1661\" data-start=\"1597\"\u003ehigh-output big block engines with raw water cooling systems\u003c\/strong\u003e\u003c\/p\u003e\n\u003chr data-end=\"1666\" data-start=\"1663\"\u003e\n\u003ch2 data-end=\"1705\" data-start=\"1668\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"1703\" data-start=\"1671\"\u003eSerial Number Fitment Notice\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp data-end=\"1726\" data-start=\"1706\"\u003eThermostats vary by:\u003c\/p\u003e\n\u003cul data-end=\"1809\" data-start=\"1727\"\u003e\n\u003cli data-end=\"1766\" data-start=\"1727\"\u003eTemperature rating (160° vs others)\u003c\/li\u003e\n\u003cli data-end=\"1785\" data-start=\"1767\"\u003eHousing design\u003c\/li\u003e\n\u003cli data-end=\"1809\" data-start=\"1786\"\u003eCooling system type\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"1899\" data-start=\"1811\"\u003e⚠️ Always confirm fitment using engine serial number or OEM part number before ordering.\u003c\/p\u003e\n\u003chr data-end=\"1904\" data-start=\"1901\"\u003e\n\u003ch2 data-end=\"1945\" data-start=\"1906\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"1945\" data-start=\"1909\"\u003eWhen This Part Needs Replacement\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp data-end=\"1987\" data-start=\"1946\"\u003eReplace the thermostat if you experience:\u003c\/p\u003e\n\u003cul data-end=\"2166\" data-start=\"1988\"\u003e\n\u003cli data-end=\"2026\" data-start=\"1988\"\u003eEngine overheating or running cold\u003c\/li\u003e\n\u003cli data-end=\"2064\" data-start=\"2027\"\u003eInconsistent temperature readings\u003c\/li\u003e\n\u003cli data-end=\"2089\" data-start=\"2065\"\u003ePoor fuel efficiency\u003c\/li\u003e\n\u003cli data-end=\"2126\" data-start=\"2090\"\u003eSlow warm-up or stuck thermostat\u003c\/li\u003e\n\u003cli data-end=\"2166\" data-start=\"2127\"\u003eCorrosion or scaling inside housing\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"2307\" data-start=\"2168\"\u003eA failed thermostat can cause the engine to run outside optimal temperature and reduce performance. \u003cspan data-state=\"closed\" class=\"\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003chr data-end=\"2312\" data-start=\"2309\"\u003e\n\u003ch2 data-end=\"2339\" data-start=\"2314\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"2339\" data-start=\"2317\"\u003eInstallation Notes\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003cul data-end=\"2539\" data-start=\"2340\"\u003e\n\u003cli data-end=\"2386\" data-start=\"2340\"\u003eReplace gasket or seal during installation\u003c\/li\u003e\n\u003cli data-end=\"2423\" data-start=\"2387\"\u003eClean mating surfaces thoroughly\u003c\/li\u003e\n\u003cli data-end=\"2458\" data-start=\"2424\"\u003eInstall in correct orientation\u003c\/li\u003e\n\u003cli data-end=\"2499\" data-start=\"2459\"\u003eConfirm 160° rating matches OEM spec\u003c\/li\u003e\n\u003cli data-end=\"2539\" data-start=\"2500\"\u003eTest engine temp after installation\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr data-end=\"2544\" data-start=\"2541\"\u003e\n\u003ch2 data-end=\"2588\" data-start=\"2546\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"2588\" data-start=\"2549\"\u003eAlternate \/ Superseded Part Numbers\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003ch3 data-end=\"2618\" data-start=\"2590\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"2618\" data-start=\"2594\"\u003eOEM Cross References\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h3\u003e\n\u003cul data-end=\"2826\" data-start=\"2619\"\u003e\n\u003cli data-end=\"2680\" data-start=\"2619\"\u003e\n\u003cstrong data-end=\"2632\" data-start=\"2621\"\u003eIndmar:\u003c\/strong\u003e S985009 \u003cspan data-state=\"closed\" class=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"2826\" data-start=\"2681\"\u003e\n\u003cstrong data-end=\"2708\" data-start=\"2683\"\u003eMercury \/ MerCruiser:\u003c\/strong\u003e\n\u003cul data-end=\"2826\" data-start=\"2713\"\u003e\n\u003cli data-end=\"2724\" data-start=\"2713\"\u003e863358T\u003c\/li\u003e\n\u003cli data-end=\"2740\" data-start=\"2727\"\u003e863358001\u003c\/li\u003e\n\u003cli data-end=\"2756\" data-start=\"2743\"\u003e8M0074922\u003c\/li\u003e\n\u003cli data-end=\"2772\" data-start=\"2759\"\u003e8M0076464\u003c\/li\u003e\n\u003cli data-end=\"2826\" data-start=\"2775\"\u003e8M0192249 \u003cspan data-state=\"closed\" class=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr data-end=\"2831\" data-start=\"2828\"\u003e\n\u003ch3 data-end=\"2869\" data-start=\"2833\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"2869\" data-start=\"2837\"\u003eAftermarket Cross References\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h3\u003e\n\u003cul data-end=\"2932\" data-start=\"2870\"\u003e\n\u003cli data-end=\"2932\" data-start=\"2870\"\u003eMallory: \u003cstrong data-end=\"2892\" data-start=\"2881\"\u003e9-43017\u003c\/strong\u003e \u003cspan data-state=\"closed\" class=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr data-end=\"2937\" data-start=\"2934\"\u003e\n\u003ch2 data-end=\"2956\" data-start=\"2939\"\u003e\u003cspan role=\"text\"\u003e\u003cstrong data-end=\"2954\" data-start=\"2942\"\u003eShipping\u003c\/strong\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp data-end=\"3022\" data-start=\"2957\"\u003eShipping: Ships same or next day for fast Canada wide shipping. ⚓\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":43564241813540,"sku":"SIE-18-43017","price":46.93,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0743\/5799\/7604\/files\/SIE-18-43017.png?v=1771568343","url":"https:\/\/marisolmarine.com\/products\/sierra-thermostat-sie-18-43017-indmar","provider":"Marisol Marine Company","version":"1.0","type":"link"}