{"title":"MerCruiser 4-Stroke 7.4L Marine Engine Parts","description":"\u003csection id=\"hero\" style=\"padding:16px 0;\"\u003e\n  \u003cp style=\"max-width:900px;\"\u003eThis page is dedicated to MerCruiser 4‑Stroke 7.4L marine engines. Use it to find compatible parts and practical service information. You’ll find maintenance tips, common replacement parts, and troubleshooting guidance below. You can also browse the main MerCruiser collection, and at the bottom of this page you’ll find links to start browsing parts for this engine. On the collection page, use the Filter \u0026amp; Sort controls to narrow results by horsepower, year range, and part category.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser\" style=\"display:inline-block;padding:10px 16px;border:1px solid #1e4; border-radius:6px; text-decoration:none;\"\u003eBrowse All MerCruiser Parts\u003c\/a\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"identify-model\" style=\"padding:16px 0;\"\u003e\n  \u003ch2\u003eHow to Identify Your 7.4L Model\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eLocate the serial\/model plate on the engine (often near the flame arrestor or on the starboard side of the block). Additional identification may be on the transom assembly.\u003c\/li\u003e\n    \u003cli\u003eDecode key options: drive family (Alpha or Bravo), fuel system (carbureted, EFI, or MPI), and cooling type (raw‑water or closed cooling). Suffix letters indicate revisions.\u003c\/li\u003e\n    \u003cli\u003ePlatform cues: 7.4L units are V8s with two rocker covers; exhaust manifolds\/elbows sit outboard. Many pair with Bravo drives and an engine‑mounted raw‑water pump.\u003c\/li\u003e\n    \u003cli\u003eRecord the full serial number before ordering; it ensures the correct ignition, cooling, and exhaust components.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"engine-overview\" style=\"padding:16px 0;\"\u003e\n  \u003ch2\u003eEngine Overview\u003c\/h2\u003e\n  \u003ch3\u003e7.4L V8 Platform\u003c\/h3\u003e\n  \u003ctable style=\"max-width:980px;border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eV8, 4‑stroke; commonly carbureted, EFI, or MPI. Often matched to Bravo drives; raw‑water or closed‑cooling variants exist.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e7.4L\/454‑cid families across multiple years; carb, EFI, and MPI trims with various ignition and cooling packages.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eHigh torque output, broad parts availability, strong charging capacity, durable drivetrain options.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eConfirm fuel system and cooling type when selecting filters, pumps, thermostats, and exhaust components. Raw‑water impellers and manifolds\/elbows are periodic wear items.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"service-kits\" style=\"padding:16px 0;\"\u003e\n  \u003ch2\u003eRoutine Maintenance \u0026amp; Service Parts\u003c\/h2\u003e\n  \u003cp style=\"max-width:900px;\"\u003eIntervals below are general guidelines for 4‑stroke MerCruiser sterndrives. Always follow the official service manual for your exact model, drive, and operating conditions.\u003c\/p\u003e\n  \u003ctable style=\"max-width:980px;border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eItem\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eInterval*\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eRemarks\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eParts Link\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eEngine oil + filter\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eWarm engine, drain completely; replace filter and confirm viscosity\/quantity.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-oil-filters\"\u003eMerCruiser Oil Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eGear oil (sterndrive)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eInspect for water intrusion and metal; pressure\/vacuum test if contamination is found.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-service-maintenance-kits\"\u003eMerCruiser Service \u0026amp; Maintenance Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eSpark plugs\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eInspect at 100 hours; replace as needed\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eSet correct gap; replace worn\/fouled plugs to improve starting and idle.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/spark-plug\"\u003eSpark Plug\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eFuel filter \/ water separator\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eDrain and inspect for water\/debris; replace cartridge or inline filter.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-fuel-filters\"\u003eMerCruiser Fuel Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eRaw‑water impeller \/ pump kit\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eEvery 1–2 seasons (or ~200 hrs)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eReplace sooner after overheating or sandy\/silty operation.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-impellers\"\u003eMerCruiser Impellers\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eAnodes (zinc\/aluminum\/magnesium)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eInspect every 3 months; replace at \u0026lt;50% mass\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eMatch alloy to water type (salt, brackish, fresh); keep bonding clean.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-anodes\"\u003eMerCruiser Anodes\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eAccessory\/serpentine belt\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eInspect regularly; replace if cracked\/noisy\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eProper tension ensures alternator and circulation pump performance.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/belt\"\u003eBelt\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eThermostat\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eInspect seasonally; replace every 2–3 seasons\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eA sticking thermostat can cause rich running or overheating; verify temp spec.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser\"\u003eMerCruiser Collection\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"common-parts\" style=\"padding:16px 0;\"\u003e\n  \u003ch2\u003eFrequently Used Parts Categories\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eRoutine Service – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-service-maintenance-kits\"\u003eMerCruiser Service \u0026amp; Maintenance Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCooling System – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-impellers\"\u003eMerCruiser Impellers\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eFuel System – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-fuel-filters\"\u003eMerCruiser Fuel Filters\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eIgnition \/ Electrical – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-alternators\"\u003eMerCruiser Alternators\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCorrosion Protection – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-anodes\"\u003eMerCruiser Anodes\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eBelts \u0026amp; Pulleys – \u003ca href=\"https:\/\/seasierra.com\/collections\/belt\"\u003eBelt\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003ePropellers \u0026amp; Hubs – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-propellers\"\u003eMerCruiser Propellers\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eGaskets \u0026amp; Seals – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-gaskets\"\u003eMerCruiser Gaskets\u003c\/a\u003e\n\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"troubleshooting\" style=\"padding:16px 0;\"\u003e\n  \u003ch2\u003eCommon Symptoms \u0026amp; Quick Checks\u003c\/h2\u003e\n  \u003ctable style=\"max-width:980px;border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eSymptom\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eCheck First\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ccc; padding:8px 6px;\"\u003eRelated Parts\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eOverheat alarm \/ weak water stream\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eInspect raw‑water impeller, belt tension, intake screens\/hoses, and thermostat operation.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eWater pump impeller kit, thermostat (see \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-impellers\"\u003eMerCruiser Impellers\u003c\/a\u003e), \u003ca href=\"https:\/\/seasierra.com\/collections\/hoses\"\u003eHoses\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/belt\"\u003eBelt\u003c\/a\u003e.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003ePoor acceleration \/ power loss\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eReplace fuel\/water‑separating filter; verify spark plug condition and timing\/advance; check restricted exhaust elbows.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\n\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-fuel-filters\"\u003eFuel filter\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/spark-plug\"\u003eSpark plugs\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-propellers\"\u003ePropeller\u003c\/a\u003e.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eHard starting \/ rough idle\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eConfirm fresh fuel, correct choke\/IAC function, clean flame arrestor, and no vacuum leaks.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\n\u003ca href=\"https:\/\/seasierra.com\/collections\/spark-plug\"\u003eSpark plugs\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-gaskets\"\u003eGaskets\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/hoses\"\u003eHoses\u003c\/a\u003e.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eGearcase noise \/ metal in gear oil\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eDrain and inspect lube; check prop for fishing line; pressure\/vacuum test the drive.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\n\u003ca href=\"https:\/\/seasierra.com\/collections\/lower-unit-seal-kits\"\u003eLower Unit Seal Kits\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/bearings\"\u003eBearings\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-propellers\"\u003ePropeller\u003c\/a\u003e.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eBattery not charging\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003eCheck belt tension, alternator output, wiring, and fuses\/breakers.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px 6px;\"\u003e\n\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-alternators\"\u003eAlternator\u003c\/a\u003e, \u003ca href=\"https:\/\/seasierra.com\/collections\/belt\"\u003eBelt\u003c\/a\u003e.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"faq\" style=\"padding:16px 0;\"\u003e\n  \u003ch2\u003eFAQs\u003c\/h2\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eAre parts interchangeable between different 7.4L years or trims?\u003c\/summary\u003e\n    \u003cp\u003eSome accessories cross over, but core items (ignition, fuel, cooling, exhaust) vary by serial number, fuel system (carb\/EFI\/MPI), drive family, and cooling type. Verify by serial before ordering.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhen should the raw‑water impeller be replaced?\u003c\/summary\u003e\n    \u003cp\u003eTypically every 1–2 seasons (about 200 hours), and sooner after any overheating or sandy\/silty use. Annual inspection is recommended.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should sterndrive gear oil be changed?\u003c\/summary\u003e\n    \u003cp\u003eAs a general rule, every 100 hours or annually. Inspect for water intrusion and metal particles; service seals if contamination is found.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat information do you need to confirm part compatibility?\u003c\/summary\u003e\n    \u003cp\u003eHave the engine serial number, drive family (Alpha\/Bravo), fuel system (carb\/EFI\/MPI), cooling type (raw\/closed), and photos of the nameplate\/part if possible.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"cta\" style=\"padding:16px 0;\"\u003e\n  \u003cp\u003eReady to find the exact parts for your MerCruiser? Browse the main collection and filter by horsepower, year, and model to narrow your results.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser\" style=\"display:inline-block;padding:10px 16px;border:1px solid #1e4; border-radius:6px; text-decoration:none;\"\u003eShop MerCruiser Parts\u003c\/a\u003e\n  \u003cp style=\"margin-top:8px;color:#444;\"\u003eIf you’re unsure about your model, send us a photo of the nameplate and the part you need and we’ll help verify compatibility.\u003c\/p\u003e\n\u003c\/section\u003e","products":[{"product_id":"thermostat-kit-160-fits-mercruiser-v6-v8-engines-replaces-807252q5","title":"Thermostat Kit, 140° – Fits MerCruiser Applications (Replaces 807252Q5 and 807252T8)","description":"\u003csection\u003e\n\u003c!-- 🔧 Table Styles (include only once per page) --\u003e\n\u003cstyle\u003e\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\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  table.ss-table th {\n    white-space:nowrap;\n    word-break:normal;\n    letter-spacing:normal;\n    font-weight:600;\n    background:#f8fafc;\n  }\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\u003e140° thermostat kit\u003c\/strong\u003e is a replacement cooling-system service kit for selected MerCruiser inboard and sterndrive applications. It is associated with Mercury Marine reference numbers \u003cstrong\u003e807252Q5\u003c\/strong\u003e and \u003cstrong\u003e807252T8\u003c\/strong\u003e, and is cross-referenced in the Sierra catalog as thermostat kit \u003cstrong\u003e18-3647\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cp\u003eThe kit helps restore the thermostat and gasket arrangement used by the original cooling system. Because MerCruiser fitment can vary by engine configuration and serial-number range, compare the existing thermostat, gasket layout, and engine identification details before ordering.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eAftermarket thermostat kit for selected MerCruiser cooling systems.\u003c\/li\u003e\n  \u003cli\u003e140°F temperature rating as listed for the related thermostat application.\u003c\/li\u003e\n  \u003cli\u003eKit format includes the thermostat and multiple housing or cover gaskets for service installation.\u003c\/li\u003e\n  \u003cli\u003eUse the reference numbers and component list below to confirm compatibility.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eThese are reference numbers associated with this thermostat kit. They should be used for identification and cross-reference only; always confirm the complete engine application before installation.\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 or Catalog\u003c\/th\u003e\n        \u003cth\u003eReference Number\u003c\/th\u003e\n        \u003cth\u003eReference Type\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury Marine\u003c\/td\u003e\n        \u003ctd\u003e807252Q5\u003c\/td\u003e\n        \u003ctd\u003eReplacement reference\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury Marine\u003c\/td\u003e\n        \u003ctd\u003e807252T8\u003c\/td\u003e\n        \u003ctd\u003eReplacement reference\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-3647\u003c\/td\u003e\n        \u003ctd\u003eThermostat kit reference\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eEngine and Model Compatibility\u003c\/h2\u003e\n\u003cp\u003eThis kit is intended for selected MerCruiser cooling-system applications associated with the references above. The available catalog information does not establish one universal year, horsepower, or serial-number range for every MerCruiser V6 or V8 engine. Confirm the engine model, cooling-system configuration, and serial-number range against the service manual or the original part before purchase.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Engine and Model Compatibility\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eApplication\u003c\/th\u003e\n        \u003cth\u003eCooling-System Use\u003c\/th\u003e\n        \u003cth\u003eTemperature\u003c\/th\u003e\n        \u003cth\u003eReference Numbers\u003c\/th\u003e\n        \u003cth\u003eFitment Note\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSelected MerCruiser inboard and sterndrive applications\u003c\/td\u003e\n        \u003ctd\u003eVerify against the original thermostat and gasket arrangement\u003c\/td\u003e\n        \u003ctd\u003e140°F\u003c\/td\u003e\n        \u003ctd\u003e807252Q5, 807252T8, 18-3647\u003c\/td\u003e\n        \u003ctd\u003eModel, year, configuration, and serial range must be confirmed before installation\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cdl\u003e\n  \u003cdt\u003eProduct Type\u003c\/dt\u003e\n  \u003cdd\u003eThermostat kit with housing and cover gaskets\u003c\/dd\u003e\n  \u003cdt\u003eTemperature Rating\u003c\/dt\u003e\n  \u003cdd\u003e140°F\u003c\/dd\u003e\n  \u003cdt\u003eApplication\u003c\/dt\u003e\n  \u003cdd\u003eSelected MerCruiser cooling-system applications\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n  \u003cdd\u003eReplacement service installation using the original housing and fasteners\u003c\/dd\u003e\n  \u003cdt\u003eKit Reference\u003c\/dt\u003e\n  \u003cdd\u003eSierra 18-3647\u003c\/dd\u003e\n  \u003cdt\u003eReplacement References\u003c\/dt\u003e\n  \u003cdd\u003eMercury Marine 807252Q5 and 807252T8\u003c\/dd\u003e\n  \u003cdt\u003eFitment Limitation\u003c\/dt\u003e\n  \u003cdd\u003eConfirm model, cooling-system configuration, and serial-number range before ordering\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\u003cp\u003eCatalog-listed components for the 18-3647 kit include:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e1 x Thermostat, reference 18-3551\u003c\/li\u003e\n  \u003cli\u003e1 x Thermostat housing gasket, reference 18-2917\u003c\/li\u003e\n  \u003cli\u003e1 x Thermostat cover gasket, reference 18-2844\u003c\/li\u003e\n  \u003cli\u003e1 x Thermostat cover gasket, reference 18-2553\u003c\/li\u003e\n  \u003cli\u003e1 x Thermostat cover gasket, reference 18-2834\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eGasket shapes and openings must match the housing being serviced. Do not combine gaskets from a different thermostat kit or application.\u003c\/p\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eAllow the engine to cool completely before beginning work. Follow the manufacturer's safety procedures.\u003c\/li\u003e\n  \u003cli\u003eDisconnect the battery if required by the service procedure and close or isolate any water or coolant supply as appropriate.\u003c\/li\u003e\n  \u003cli\u003eLocate the thermostat housing and drain enough coolant or water to prevent spillage during removal.\u003c\/li\u003e\n  \u003cli\u003eRemove the housing or cover fasteners and carefully separate the mating surfaces.\u003c\/li\u003e\n  \u003cli\u003eRemove the old thermostat and gasket material. Record the thermostat orientation before removal.\u003c\/li\u003e\n  \u003cli\u003eClean the mating surfaces without damaging the housing or engine sealing faces.\u003c\/li\u003e\n  \u003cli\u003eInstall the new thermostat in the same orientation as the original and select the gasket that matches the housing configuration.\u003c\/li\u003e\n  \u003cli\u003eReassemble the housing and tighten the fasteners to the engine manufacturer's specified torque.\u003c\/li\u003e\n  \u003cli\u003eRestore the cooling system, start the engine, and check operating temperature and the housing area for leaks.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting and FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat temperature thermostat does this kit use?\u003c\/summary\u003e\n  \u003cp\u003eThe related thermostat application is listed at \u003cstrong\u003e140°F\u003c\/strong\u003e. Confirm that this temperature rating matches your engine's required specification before installation.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat part numbers does this kit replace?\u003c\/summary\u003e\n  \u003cp\u003eThe catalog reference for this kit lists Mercury Marine numbers \u003cstrong\u003e807252Q5\u003c\/strong\u003e and \u003cstrong\u003e807252T8\u003c\/strong\u003e. Sierra catalog reference \u003cstrong\u003e18-3647\u003c\/strong\u003e identifies the thermostat kit.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWill this fit every MerCruiser V6 or V8 engine?\u003c\/summary\u003e\n  \u003cp\u003eNo universal V6 or V8 fitment should be assumed. MerCruiser applications vary by model, cooling-system configuration, and serial-number range. Compare your original components and verify the service-manual application before ordering.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhy are several gaskets included?\u003c\/summary\u003e\n  \u003cp\u003eThe kit covers the gasket arrangement associated with the listed application. Use only the gasket or gaskets that match your thermostat housing and cover. Do not install every gasket automatically if the original configuration uses a different arrangement.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are common symptoms of a thermostat problem?\u003c\/summary\u003e\n  \u003cp\u003ePossible symptoms include overheating, unstable operating temperature, slow warm-up, or coolant or water leakage near the thermostat housing. These symptoms can also be caused by an impeller, hose, heat exchanger, exhaust-manifold, or cooling-passage problem, so inspect the complete cooling system.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eIs this an OEM component?\u003c\/summary\u003e\n  \u003cp\u003eThis listing is for an aftermarket replacement kit. Mercury Marine and Sierra numbers are provided as reference numbers for identification and cross-reference, not as a statement that the replacement is manufactured by Mercury Marine or Sierra.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003ch2\u003eSafety and Important Information\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify the engine model, serial-number range, cooling-system configuration, and original gasket layout before ordering.\u003c\/li\u003e\n  \u003cli\u003eDo not rely on horsepower, displacement, or model-family names alone to confirm fitment.\u003c\/li\u003e\n  \u003cli\u003eInstall only after the engine has cooled and follow the applicable marine service procedure.\u003c\/li\u003e\n  \u003cli\u003eUse the correct gasket for the housing being serviced and inspect all sealing surfaces before reassembly.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended when the application or cooling-system configuration is uncertain.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eAbout Sea Sierra\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMarine Parts Selection\u003c\/strong\u003e — We supply replacement components for a range of marine cooling and engine-service applications.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eApplication-Focused Information\u003c\/strong\u003e — Reference numbers and component details are provided to help customers compare replacement parts accurately.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSupport for Installation Planning\u003c\/strong\u003e — Always confirm model and serial-number details before ordering or beginning service.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50723970842939,"sku":"20TH008","price":35.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/20TH008_1_71b85ee8-9c19-455b-95b6-c1b554877e98.jpg?v=1763038812"}],"url":"https:\/\/seasierra.com\/collections\/mercruiser-4-stroke-7-4l-marine-engine-parts.oembed","provider":"SeaSierra","version":"1.0","type":"link"}