{"product_id":"thermostat-kit-fits-mercury-mariner-4-stroke-8-40-hp-replaces-825212a1-825212001-855676003","title":"Thermostat Kit – Fits Mercury\/Mariner 4-Stroke 8-40 HP (Replaces 825212A1, 825212001, 855676003)","description":"\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\u003csection\u003e\n  \u003ch2\u003eProduct Details\u003c\/h2\u003e\n  \u003cp\u003eThis \u003cstrong\u003eThermostat Kit – Fits Mercury\/Mariner 4-Stroke 8-40 HP Outboard Motors\u003c\/strong\u003e is an essential component for maintaining optimal engine temperature in Mercury\/Mariner 4-Stroke 8–40 HP outboard engines from 1995–2018, including specific 30 HP (1999–2005), 40 HP (1998–2018), and 50 HP (1995–2000) models.\u003c\/p\u003e\n  \u003cp\u003eIt serves as a direct cross-reference for multiple OEM and aftermarket part numbers, including Mercury 825212A1, 825212001, 855676003, 825212T02, 855676A1, and Sierra 18-3642.\u003c\/p\u003e\n  \u003cul\u003e\n    \u003cli\u003eEngineered for direct-fit installation.\u003c\/li\u003e\n    \u003cli\u003eFeatures a 140°F (60°C) temperature rating.\u003c\/li\u003e\n    \u003cli\u003eIncludes the thermostat, rubber seal, and housing gasket for a complete service.\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\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e825212001\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e855676003\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e825212T02\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e855676A1\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eSierra\u003c\/td\u003e\n          \u003ctd\u003e18-3642\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\u003eFor Mercury\/Mariner engines, verify your model, horsepower, and serial number range against the data provided to ensure an exact match.\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\u003e8HP (Bodensee)\u003c\/td\u003e\n          \u003ctd\u003e8\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P086824-0P400999\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e9.9HP\u003c\/td\u003e\n          \u003ctd\u003e9.9\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e1995–1998\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003e232cc engine\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e9.9HP\u003c\/td\u003e\n          \u003ctd\u003e9.9\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e1999–2004\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003e323cc engine, Serial: 0P075166-0P400999\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e13.5HP (International)\u003c\/td\u003e\n          \u003ctd\u003e13.5\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P134638\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e15HP\u003c\/td\u003e\n          \u003ctd\u003e15\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P9973100 \u0026amp; UP\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e25HP\u003c\/td\u003e\n          \u003ctd\u003e25\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P9973100 \u0026amp; UP\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e30HP\u003c\/td\u003e\n          \u003ctd\u003e30\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e1999–2005\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eUSA made (0G760300-1B226999), Belgium made (0P017000-0P400999)\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e30HP (Carb) (3 Cyl) (EFI)\u003c\/td\u003e\n          \u003ctd\u003e30\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P153500-0P400999\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e40HP\u003c\/td\u003e\n          \u003ctd\u003e40\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e1998–2018\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 994408 \u0026amp; UP\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e40HP (Carb) (3 Cyl)\u003c\/td\u003e\n          \u003ctd\u003e40\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P153500-0P400999\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e40HP (EFI) (3 Cyl)\u003c\/td\u003e\n          \u003ctd\u003e40\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P401000-0P400999\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e40HP (ITALY)\u003c\/td\u003e\n          \u003ctd\u003e40\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 0P017000-0P094499\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e45HP (Bodensee)\u003c\/td\u003e\n          \u003ctd\u003e45\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 9944807 \u0026amp; UP\u003c\/td\u003e\n        \u003c\/tr\u003e\n        \u003ctr\u003e\n          \u003ctd\u003eMercury\u003c\/td\u003e\n          \u003ctd\u003e50HP (BIGFOOT)\u003c\/td\u003e\n          \u003ctd\u003e50\u003c\/td\u003e\n          \u003ctd\u003e4-Stroke\u003c\/td\u003e\n          \u003ctd\u003e1995–2000\u003c\/td\u003e\n          \u003ctd\u003e825212A1\u003c\/td\u003e\n          \u003ctd\u003eSerial: 9944807 \u0026amp; UP, USA made (0G231123-0T178499)\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 replacement\u003c\/dd\u003e\n    \u003cdt\u003eTemperature Rating\u003c\/dt\u003e\n\u003cdd\u003e140°F (60°C)\u003c\/dd\u003e\n    \u003cdt\u003eFuel Type\u003c\/dt\u003e\n\u003cdd\u003eGasoline\u003c\/dd\u003e\n    \u003cdt\u003eMounting Type\u003c\/dt\u003e\n\u003cdd\u003eEngine Mount\u003c\/dd\u003e\n    \u003cdt\u003eWeight\u003c\/dt\u003e\n\u003cdd\u003e0.03 kg (1.13 oz)\u003c\/dd\u003e\n    \u003cdt\u003eOther Technical Attributes\u003c\/dt\u003e\n\u003cdd\u003eFor manual operation\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 (825212A1)\u003c\/li\u003e\n    \u003cli\u003e1 x Ring Rubber Seal\u003c\/li\u003e\n    \u003cli\u003e1 x Housing Gasket (27-824853)\u003c\/li\u003e\n    \u003cli\u003e1 x Installation Instructions\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n  \u003col\u003e\n    \u003cli\u003eEnsure the engine is completely cool and disconnect the negative battery terminal for safety.\u003c\/li\u003e\n    \u003cli\u003eLocate the thermostat housing on the engine. Place a drain pan underneath to catch any spilling coolant.\u003c\/li\u003e\n    \u003cli\u003eCarefully remove the bolts securing the housing cover. Gently tap the cover if needed to break the seal.\u003c\/li\u003e\n    \u003cli\u003eRemove the old thermostat and gaskets. Take note of the thermostat's orientation.\u003c\/li\u003e\n    \u003cli\u003eThoroughly clean the mating surfaces of the housing and the engine block, removing all old gasket material.\u003c\/li\u003e\n    \u003cli\u003eInstall the new thermostat from the kit in the correct orientation.\u003c\/li\u003e\n    \u003cli\u003ePlace the new gasket and seal in position and reinstall the housing cover.\u003c\/li\u003e\n    \u003cli\u003eTighten the bolts evenly to the manufacturer's specified torque to ensure a proper seal.\u003c\/li\u003e\n    \u003cli\u003eReconnect the battery, refill the cooling system with the appropriate coolant, and check for leaks.\u003c\/li\u003e\n    \u003cli\u003eStart the engine, let it reach operating temperature, and re-check for any leaks.\u003c\/li\u003e\n  \u003c\/ol\u003e\n\n  \u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow do I know if my thermostat is failing?\u003c\/summary\u003e\n    \u003cp\u003eCommon signs include engine overheating, the engine not reaching normal operating temperature (running too cool), erratic temperature gauge readings, or coolant leaks from the thermostat housing area.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhy is there a temperature difference listed (120°F vs. 140°F)?\u003c\/summary\u003e\n    \u003cp\u003eDifferent aftermarket sources sometimes report conflicting data. This thermostat is rated at 140°F (60°C), a specification confirmed by multiple retailers for this application. For certainty, always compare with your engine's service manual recommendation.\u003c\/p\u003e\n  \u003c\/details\u003e\n    \u003cdetails\u003e\n    \u003csummary\u003eWhat is the recommended replacement interval for a thermostat?\u003c\/summary\u003e\n    \u003cp\u003eThermostats are a preventative maintenance item. It's wise to inspect them during regular service and consider replacement every 200-300 hours or 2-3 years, especially when operating in saltwater environments.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs this kit compatible with both Mercury and Mariner branded engines?\u003c\/summary\u003e\n    \u003cp\u003eYes, it is designed for a wide range of both Mercury and Mariner 4-stroke outboards within the specified HP and year range. Double-check the compatibility table for your exact model and serial number to confirm fitment.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDo I need to use sealant on the new gaskets?\u003c\/summary\u003e\n    \u003cp\u003eThe included gaskets are typically designed to be installed dry. However, it is best practice to consult your engine's official service manual for specific instructions regarding the use of gasket sealants.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat's the difference between OEM and aftermarket parts?\u003c\/summary\u003e\n    \u003cp\u003eThis listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. Our parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow fast is shipping and what does it cost?\u003c\/summary\u003e\n    \u003cp\u003eWe ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free to most locations; expedited options and costs are shown at checkout where available.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat is the warranty and return policy?\u003c\/summary\u003e\n    \u003cp\u003eThis part is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in original condition. See our policy page or reach out for instructions.\u003c\/p\u003e\n  \u003c\/details\u003e\n\n  \u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eVerify images and specifications against 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 quality control.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50718267867451,"sku":"825212A1-QM","price":17.8,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/825212A1-QM.png?v=1762958608","url":"https:\/\/seasierra.com\/products\/thermostat-kit-fits-mercury-mariner-4-stroke-8-40-hp-replaces-825212a1-825212001-855676003","provider":"SeaSierra","version":"1.0","type":"link"}