{"product_id":"thermostat-kit-fits-mercury-mariner-70-125-hp-2-stroke-replaces-803061t1","title":"Thermostat Kit – Fits Mercury\/Mariner 70-125 HP 2-Stroke (Replaces 803061T1)","description":"\u003csection\u003e\n\u003c!-- 🔧 Table Styles (include only once per page) --\u003e\n\u003cstyle\u003e\n  \/* Outer container allows horizontal scrolling (with iOS momentum) *\/\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\n\n  \/* Base table styles *\/\n  table.ss-table { width:100%; border-collapse:collapse; min-width:640px; }\n  table.ss-table th, table.ss-table td {\n    padding:10px 12px; border:1px solid #e5e7eb; text-align:left; vertical-align:top;\n  }\n\n  \/* Key: prevent wrapping, word breaks, and vertical text in headers *\/\n  table.ss-table th {\n    white-space:nowrap;       \/* Do not wrap *\/\n    word-break:normal;        \/* Don’t break words *\/\n    letter-spacing:normal;    \/* Prevent theme styles from stretching letters *\/\n    font-weight:600;\n    background:#f8fafc;\n  }\n\n  \/* Small screen optimization *\/\n  @media (max-width:480px){\n    table.ss-table th, table.ss-table td { padding:8px 10px; font-size:14px; }\n  }\n\u003c\/style\u003e\n\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis \u003cstrong\u003eThermostat Kit – Fits Mercury\/Mariner 70-125 HP 2-Stroke (Replaces 803061T1)\u003c\/strong\u003e provides a reliable, direct-fit replacement for maintaining the cooling system on inline 3 \u0026amp; 4 cylinder outboards from 1987 and newer. Engineered to regulate engine temperature, this kit ensures your motor operates within its optimal temperature range, preventing both overheating and overcooling.\u003c\/p\u003e\n\u003cp\u003eThis component is a direct interchange for Sierra 18-3569, Sierra 18-3549\/18-0339, GLM 13124, Mallory 9-43155\/9-43014\/9-60004, and GHmarine 18-3569.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eEngineered as a direct OEM-equivalent replacement.\u003c\/li\u003e\n\u003cli\u003eEssential for routine cooling system maintenance and repair.\u003c\/li\u003e\n\u003cli\u003eIncludes thermostat, seal, gasket, and washer for a complete installation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eUse this matrix to confirm equivalent references across OEM and aftermarket.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Part Number Matrix\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eBrand\u003c\/th\u003e\n        \u003cth\u003ePart Number\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-3569\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-3549\/18-0339\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eGLM\u003c\/td\u003e\n        \u003ctd\u003e13124\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMallory\u003c\/td\u003e\n        \u003ctd\u003e9-43155\/9-43014\/9-60004\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eGHmarine\u003c\/td\u003e\n        \u003ctd\u003e18-3569\u003c\/td\u003e\n      \u003c\/tr\u003e\n\t  \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eEngine \u0026amp; Model Compatibility\u003c\/h2\u003e\n\u003cp\u003eConfirm your engine model\/year in the table below.\u003c\/p\u003e\n\u003cp\u003eFits Mercury\/Mariner 2-stroke inline 3 \u0026amp; 4 cylinder outboards from 1987 and newer.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Engine \u0026amp; Model Compatibility\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eBrand\u003c\/th\u003e\n        \u003cth\u003eModel\u003c\/th\u003e\n        \u003cth\u003eRated HP\u003c\/th\u003e\n        \u003cth\u003eStroke\u003c\/th\u003e\n        \u003cth\u003eYears\u003c\/th\u003e\n        \u003cth\u003eOEM Part No.\u003c\/th\u003e\n        \u003cth\u003eNotes\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e70\u003c\/td\u003e\n        \u003ctd\u003e70\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1987+ (A996142 \u0026amp; UP)\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n        \u003ctd\u003e3 Cylinder\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e75\u003c\/td\u003e\n        \u003ctd\u003e75\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1990+ (C222000 \u0026amp; UP)\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n        \u003ctd\u003e3 Cylinder\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e80\u003c\/td\u003e\n        \u003ctd\u003e80\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1987–1990 (A996142 \u0026amp; UP)\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n        \u003ctd\u003e3 Cylinder\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e90\u003c\/td\u003e\n        \u003ctd\u003e90\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1987–2007+ (A996142 \u0026amp; UP)\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n        \u003ctd\u003e3 Cylinder\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e100\u003c\/td\u003e\n        \u003ctd\u003e100\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1987+ (B209468 \u0026amp; UP)\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n        \u003ctd\u003e4 Cylinder\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e115\u003c\/td\u003e\n        \u003ctd\u003e115\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1987+ (C100000 \u0026amp; UP)\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n        \u003ctd\u003e4 Cylinder\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e125\u003c\/td\u003e\n        \u003ctd\u003e125\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1987+ (D283222 \u0026amp; UP)\u003c\/td\u003e\n        \u003ctd\u003e803061T1\u003c\/td\u003e\n        \u003ctd\u003e4 Cylinder\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specs\u003c\/h2\u003e\n\u003cdl\u003e\n  \u003cdt\u003eProduct Type\u003c\/dt\u003e\n\u003cdd\u003eThermostat Kit\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n\u003cdd\u003eDirect OEM replacement\u003c\/dd\u003e\n  \u003cdt\u003eTemperature Rating\u003c\/dt\u003e\n\u003cdd\u003e122°F \/ 50°C (primary); some sources indicate 120°F\u003c\/dd\u003e\n  \u003cdt\u003eHousing Material\u003c\/dt\u003e\n\u003cdd\u003eBrass\/Copper (thermostat), Metal (housing components)\u003c\/dd\u003e\n  \u003cdt\u003eHousing Color\u003c\/dt\u003e\n\u003cdd\u003eCopper\/Brass with Black\/Gray Gaskets\u003c\/dd\u003e\n  \u003cdt\u003eOperating Temperature\u003c\/dt\u003e\n\u003cdd\u003e122°F \/ 50°C (opening temperature)\u003c\/dd\u003e\n  \u003cdt\u003eWarranty\u003c\/dt\u003e\n\u003cdd\u003e1 Year (aftermarket versions)\u003c\/dd\u003e\n  \u003cdt\u003eOther Technical Attributes\u003c\/dt\u003e\n\u003cdd\u003eFor cooling system maintenance\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e1 x Thermostat (14586)\u003c\/li\u003e\n  \u003cli\u003e1 x Thermostat Seal (62386001)\u003c\/li\u003e\n  \u003cli\u003e1 x Thermostat Cover Gasket (430068)\u003c\/li\u003e\n  \u003cli\u003e1 x Washer (47533)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eEnsure the engine is off and cool. Disconnect the battery.\u003c\/li\u003e\n  \u003cli\u003eLocate the thermostat housing on the engine block.\u003c\/li\u003e\n  \u003cli\u003ePlace a drain pan below the housing and remove the drain plug, if equipped, to drain coolant from the powerhead.\u003c\/li\u003e\n  \u003cli\u003eLoosen and remove the bolts securing the thermostat cover.\u003c\/li\u003e\n  \u003cli\u003eCarefully remove the cover, old gasket, and the old thermostat. Note the orientation of the thermostat.\u003c\/li\u003e\n  \u003cli\u003eClean the mating surfaces of the housing and cover, removing all old gasket material.\u003c\/li\u003e\n  \u003cli\u003eInstall the new thermostat in the correct orientation, followed by the new seal and gasket.\u003c\/li\u003e\n  \u003cli\u003eReinstall the cover and tighten the bolts to the manufacturer's specified torque.\u003c\/li\u003e\n  \u003cli\u003eRefill the cooling system. Reconnect the battery.\u003c\/li\u003e\n  \u003cli\u003eStart the engine and check for leaks and proper operating temperature.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\u003csummary\u003eHow do I know if this thermostat kit fits my engine?\u003c\/summary\u003e\u003cp\u003eFirst, check the compatibility table and match your engine's brand, model, horsepower, and year or serial number range. It is critical to also visually compare the parts in the photos to your existing thermostat and housing to ensure a perfect match before ordering.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWhat are the signs of a failing outboard thermostat?\u003c\/summary\u003e\u003cp\u003eA thermostat can fail stuck open or stuck closed. A stuck-open thermostat will cause the engine to run too cool, leading to poor performance and fuel economy. A stuck-closed thermostat will cause the engine to overheat, which can result in serious damage. An alarm horn or fluctuating temperature gauge are key indicators.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWhen should I replace my thermostat?\u003c\/summary\u003e\u003cp\u003eIt's good practice to replace the thermostat as part of routine cooling system maintenance, especially every few years in saltwater environments. You should replace it immediately if you notice any signs of engine overheating or incorrect operating temperature.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWhat temperature does this thermostat open at?\u003c\/summary\u003e\u003cp\u003eThis thermostat is rated to begin opening at approximately 122°F (50°C). Minor variations in temperature ratings (e.g., 120°F) exist across different aftermarket sources, but performance is functionally identical.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eIs this a complete kit for the job?\u003c\/summary\u003e\u003cp\u003eThis kit includes the thermostat, thermostat seal, cover gasket, and washer, which are the essential components for a standard replacement. You may need additional tools and sealant depending on your engine's condition.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWhy do some kits for the same part number show different contents?\u003c\/summary\u003e\u003cp\u003eWhile the core thermostat is the same, some aftermarket manufacturers may bundle slightly different gaskets or hardware. The components listed in \"What's in the Box\" are exactly what you will receive with this kit.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eOEM vs. Aftermarket?\u003c\/summary\u003e\u003cp\u003eThis listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eShipping speed \u0026amp; cost?\u003c\/summary\u003e\u003cp\u003eWe ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWarranty \u0026amp; returns?\u003c\/summary\u003e\u003cp\u003eCovered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused \u0026amp; in original condition). See our policy page or reach out for instructions.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify images\/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.\u003c\/li\u003e\n  \u003cli\u003eThis is an aftermarket replacement, not an OEM component.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended for safety and performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eAbout Sea Sierra\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePro-Grade Standards\u003c\/strong\u003e — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFast Global Fulfillment\u003c\/strong\u003e — Free standard delivery to most regions in 5–15 days.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer-Direct Value\u003c\/strong\u003e — Fair pricing without compromising on materials or QC.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50718242996539,"sku":"GH-TH23631-M","price":23.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/GH-TH23631-M.png?v=1762958087","url":"https:\/\/seasierra.com\/products\/thermostat-kit-fits-mercury-mariner-70-125-hp-2-stroke-replaces-803061t1","provider":"SeaSierra","version":"1.0","type":"link"}