{"title":"Mercury MerCruiser 4-Stroke 120-165HP Outboard Marine Engine Parts","description":"\u003csection id=\"hero\" style=\"padding:16px 0;\"\u003e\n  \u003cp\u003eThis page is for Mercury 4‑Stroke 120–165HP outboard engines. Use it to find compatible parts and practical service information, including maintenance tips, common replacement items, and troubleshooting guidance. You can also browse the main Mercury collection. Scroll to the bottom of this page to start browsing parts for this engine, and use the “Filter \u0026amp; Sort” controls on the collection to narrow results by horsepower, year range, and part category.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-outboard-parts\" style=\"display:inline-block;padding:10px 16px;border:1px solid #333;border-radius:6px;text-decoration:none;\"\u003eBrowse All Mercury 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 120–165HP Model\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eLocate the engine’s serial plate on the transom bracket or swivel bracket; it lists the serial number and power rating.\u003c\/li\u003e\n    \u003cli\u003eDecode the model\/serial details to confirm shaft length (L\/XL\/XXL), control type (tiller\/remote), and options (charging output, gearcase).\u003c\/li\u003e\n    \u003cli\u003eFor 4‑stroke models, note the engine platform: mid‑range Inline‑4 versus V6 FourStroke. Some routine parts overlap, but cooling, intake, and ignition components can differ.\u003c\/li\u003e\n    \u003cli\u003eWhen in doubt, record the full serial number and photograph the nameplate and the part you’re replacing for accurate verification.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"platforms\" style=\"padding:16px 0;\"\u003e\n  \u003ch2\u003ePlatform Overview\u003c\/h2\u003e\n  \u003ch3\u003eInline‑4 EFI FourStroke\u003c\/h3\u003e\n  \u003ctable style=\"width:100%;max-width:900px;border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eConfiguration\u003c\/td\u003e\n        \u003ctd\u003eInline‑4, EFI 4‑stroke outboard\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eCommon Models\u003c\/td\u003e\n        \u003ctd\u003eFourStroke family in the mid‑horsepower range (approx. 120–150 HP class)\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eAdvantages\u003c\/td\u003e\n        \u003ctd\u003eGood fuel economy, relatively light weight, smooth mid‑range performance\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eNotes\u003c\/td\u003e\n        \u003ctd\u003eImpellers, gearcase seals, and anodes often overlap across serial ranges; always match by serial for exact fit.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\n  \u003ch3\u003eV6 EFI FourStroke\u003c\/h3\u003e\n  \u003ctable style=\"width:100%;max-width:900px;border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eConfiguration\u003c\/td\u003e\n        \u003ctd\u003eV6, EFI 4‑stroke outboard\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eCommon Models\u003c\/td\u003e\n        \u003ctd\u003eFourStroke family overlapping the upper mid‑range (approx. 165–175 HP class)\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eAdvantages\u003c\/td\u003e\n        \u003ctd\u003eHigher charging capacity and strong thrust with robust mid‑to‑top‑end power\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eNotes\u003c\/td\u003e\n        \u003ctd\u003eRoutine‑service items can be similar to Inline‑4, but intake, ignition, and some cooling parts differ. Confirm by serial and gearcase type.\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\u003eIntervals below are general guidelines; always follow your official service manual and adjust for local conditions and usage.\u003c\/p\u003e\n  \u003ctable style=\"width:100%;max-width:1000px;border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eItem\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eInterval*\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eRemarks\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eParts Link\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eEngine oil + filter\u003c\/td\u003e\n        \u003ctd\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd\u003eUse marine‑grade 4‑stroke oil; replace the filter with each oil change\u003c\/td\u003e\n        \u003ctd\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/oil-filters\"\u003eOil Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eGear oil (lower unit)\u003c\/td\u003e\n        \u003ctd\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd\u003eInspect for water\/milky oil and metal on the drain plug magnet\u003c\/td\u003e\n        \u003ctd\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-lower-unit-seal-kits\"\u003eMercury Lower Unit Seal Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSpark plugs\u003c\/td\u003e\n        \u003ctd\u003eInspect at 100 hours; replace 200–300 hours or as needed\u003c\/td\u003e\n        \u003ctd\u003eGap to spec; replace if fouled, worn, or corroded\u003c\/td\u003e\n        \u003ctd\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/spark-plug\"\u003eSpark Plugs\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eFuel filter \/ water‑separating filter\u003c\/td\u003e\n        \u003ctd\u003eEvery 100 hours (or sooner with contaminated fuel)\u003c\/td\u003e\n        \u003ctd\u003eDrain or replace if water or debris is present\u003c\/td\u003e\n        \u003ctd\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/fuel-filters-1\"\u003eFuel Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eWater pump impeller \/ kit\u003c\/td\u003e\n        \u003ctd\u003eInspect annually; replace every 2 seasons or ~200 hours\u003c\/td\u003e\n        \u003ctd\u003eReplace sooner if telltale weakens or overheat alarms occur\u003c\/td\u003e\n        \u003ctd\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-water-pump-repair-kits\"\u003eMercury Water Pump Repair Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eAnodes (corrosion protection)\u003c\/td\u003e\n        \u003ctd\u003eInspect every 50 hours; replace when 50% depleted\u003c\/td\u003e\n        \u003ctd\u003eSelect alloy for fresh, brackish, or salt water environments\u003c\/td\u003e\n        \u003ctd\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/anodes\"\u003eAnodes\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003ePropeller \u0026amp; hardware\u003c\/td\u003e\n        \u003ctd\u003eInspect each trip; remove\/grease splines seasonally\u003c\/td\u003e\n        \u003ctd\u003eCheck for nicks, bent blades, and fishing line behind the prop hub\u003c\/td\u003e\n        \u003ctd\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/propellers\"\u003ePropellers\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n  \u003cp style=\"font-size:12px;color:#555;\"\u003e*Intervals may vary by environment and usage. Always defer to your engine’s official service schedule.\u003c\/p\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 Kits – \u003ca href=\"https:\/\/seasierra.com\/collections\/service-maintenance-kits\"\u003eService \u0026amp; Maintenance Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCooling System – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-water-pump-repair-kits\"\u003eMercury Water Pump Repair Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eFuel System – \u003ca href=\"https:\/\/seasierra.com\/collections\/fuel-filters-1\"\u003eFuel Filters\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eIgnition \u0026amp; Starting – \u003ca href=\"https:\/\/seasierra.com\/collections\/spark-plug\"\u003eSpark Plugs\u003c\/a\u003e and \u003ca href=\"https:\/\/seasierra.com\/collections\/starters\"\u003eStarters\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eGearcase Sealing – \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-lower-unit-seal-kits\"\u003eMercury Lower Unit Seal Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003ePropulsion – \u003ca href=\"https:\/\/seasierra.com\/collections\/propellers\"\u003ePropellers\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCorrosion Protection – \u003ca href=\"https:\/\/seasierra.com\/collections\/anodes\"\u003eAnodes\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=\"width:100%;max-width:1000px;border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eSymptom\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eCheck First\u003c\/th\u003e\n        \u003cth style=\"text-align:left;border-bottom:1px solid #ddd;\"\u003eRelated Parts\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eWeak telltale or overheat alarm\u003c\/td\u003e\n        \u003ctd\u003eInspect intake screens for debris, verify impeller condition, confirm thermostat operation\u003c\/td\u003e\n        \u003ctd\u003eWater pump kit, thermostat, intake screen\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003ePoor acceleration or power loss\u003c\/td\u003e\n        \u003ctd\u003eCheck prop damage\/pitch, replace fuel filter, inspect for water in fuel, verify spark plugs\u003c\/td\u003e\n        \u003ctd\u003ePropeller, fuel filter, spark plugs\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eHard starting or rough idle\u003c\/td\u003e\n        \u003ctd\u003eConfirm battery state, prime fuel system, inspect plugs and fuel lines, clean idle air control if applicable\u003c\/td\u003e\n        \u003ctd\u003eSpark plugs, fuel hoses, filters\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eGearcase noise or metal in gear oil\u003c\/td\u003e\n        \u003ctd\u003eCheck oil level\/color, inspect drain plug gaskets, look for fishing line on prop shaft, evaluate for leaking seals\u003c\/td\u003e\n        \u003ctd\u003eLower unit seal kit, bearings, drain plug gaskets\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 years or platforms?\u003c\/summary\u003e\n    \u003cp\u003eSome service items may cross over, but ignition, intake, cooling, and gearcase components often change by year, serial range, and platform (Inline‑4 vs V6). Always confirm with your full serial number.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhen should the impeller be replaced?\u003c\/summary\u003e\n    \u003cp\u003eInspect annually and replace about every two seasons or ~200 hours. Replace sooner if the telltale weakens, you run in sandy\/weedy water, or if any overheat warnings occur.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should I change the gear oil?\u003c\/summary\u003e\n    \u003cp\u003eChange lower unit gear oil every 100 hours or annually. If the oil appears milky, contains metal debris, or shows water intrusion, service the seals before further operation.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat information helps confirm part compatibility?\u003c\/summary\u003e\n    \u003cp\u003ePlease provide the engine serial number, shaft length (L\/XL\/XXL), control type (tiller\/remote), and notable options (alternator output, gearcase). Clear photos of the nameplate and the part to replace are very helpful.\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 shop by horsepower, year, and model? Browse the main Mercury collection to find parts that match your 120–165HP FourStroke outboard.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-outboard-parts\" style=\"display:inline-block;padding:10px 16px;border:1px solid #333;border-radius:6px;text-decoration:none;\"\u003eBrowse All Mercury Parts\u003c\/a\u003e\n  \u003cp style=\"margin-top:8px;color:#555;\"\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-gasket-kit-fits-mercruiser-2-5l-120hp-3-0l-140hp-replaces-59078t3-59078a1-59078q3-59078b-59078","title":"Thermostat \u0026 Gasket Kit – Fits MerCruiser 120\/140\/165 GM Engines and Chrysler Force 55\/60\/65 HP Engines, 140°F","description":"\u003csection\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 140°F (60°C) thermostat and gasket kit is a replacement cooling-system service kit for selected MerCruiser GM stern-drive engines and Chrysler Force outboard engines. It is listed for MerCruiser 120 and 140 GM applications, including 2.5L and 3.0L GM engines, the 3.0L LX, and 165 GM applications. It is also listed for Chrysler Force 55, 60, and 65 HP engines.\u003c\/p\u003e\n\u003cp\u003eThe kit combines a thermostat and the matching thermostat housing gasket for a convenient replacement during cooling-system service. Always compare the thermostat, gasket, housing, engine model, and manufacturer part number with the parts being replaced before installation.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e140°F (60°C) thermostat rating.\u003c\/li\u003e\n  \u003cli\u003eKit includes one thermostat and one thermostat gasket.\u003c\/li\u003e\n  \u003cli\u003eReference kit number: Sierra 18-3650.\u003c\/li\u003e\n  \u003cli\u003eDesigned for the listed MerCruiser GM and Chrysler Force applications.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eThe following manufacturer and aftermarket references are associated with this thermostat kit or its included components. Reference numbers do not replace confirmation of the engine model and application.\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\u003eApplication or Component\u003c\/th\u003e\n        \u003cth\u003eReference Number\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMerCruiser thermostat kit\u003c\/td\u003e\n        \u003ctd\u003e18-3650\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMerCruiser thermostat\u003c\/td\u003e\n        \u003ctd\u003e59078, 59078A1, 59078T3\/Q3, 59078B\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eIncluded thermostat\u003c\/td\u003e\n        \u003ctd\u003e18-3550\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eIncluded thermostat gasket\u003c\/td\u003e\n        \u003ctd\u003e18-2831\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eThermostat gasket reference\u003c\/td\u003e\n        \u003ctd\u003e27-47590-1\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eChrysler Force applications\u003c\/td\u003e\n        \u003ctd\u003eF85068-2, F84068-2, F85068-1, F85068\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 the manufacturer, engine rating, displacement, and original part reference before ordering. The available application information does not specify a universal year or serial-number range for every listed engine.\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\u003eBrand\u003c\/th\u003e\n        \u003cth\u003eEngine or Model\u003c\/th\u003e\n        \u003cth\u003eRated HP\u003c\/th\u003e\n        \u003cth\u003eDisplacement or Description\u003c\/th\u003e\n        \u003cth\u003eAssociated References\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMerCruiser\u003c\/td\u003e\n        \u003ctd\u003e120 GM\u003c\/td\u003e\n        \u003ctd\u003e120 HP\u003c\/td\u003e\n        \u003ctd\u003eGM application; 2.5L GM\u003c\/td\u003e\n        \u003ctd\u003e59078, 59078A1, 59078T3\/Q3, 59078B\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMerCruiser\u003c\/td\u003e\n        \u003ctd\u003e140 GM\u003c\/td\u003e\n        \u003ctd\u003e140 HP\u003c\/td\u003e\n        \u003ctd\u003e3.0L GM\u003c\/td\u003e\n        \u003ctd\u003e59078, 59078A1, 59078T3\/Q3, 59078B\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMerCruiser\u003c\/td\u003e\n        \u003ctd\u003e3.0L LX GM\u003c\/td\u003e\n        \u003ctd\u003eNot separately stated\u003c\/td\u003e\n        \u003ctd\u003e3.0L LX GM\u003c\/td\u003e\n        \u003ctd\u003e59078, 59078A1, 59078T3\/Q3, 59078B\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMerCruiser\u003c\/td\u003e\n        \u003ctd\u003e165 GM\u003c\/td\u003e\n        \u003ctd\u003e165 HP\u003c\/td\u003e\n        \u003ctd\u003eGM application\u003c\/td\u003e\n        \u003ctd\u003e59078, 59078A1, 59078T3\/Q3, 59078B\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eChrysler Force\u003c\/td\u003e\n        \u003ctd\u003eForce outboard\u003c\/td\u003e\n        \u003ctd\u003e55, 60, or 65 HP\u003c\/td\u003e\n        \u003ctd\u003eApplication-specific fitment\u003c\/td\u003e\n        \u003ctd\u003eF85068-2, F84068-2, F85068-1, F85068\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 and gasket kit\u003c\/dd\u003e\n  \u003cdt\u003eThermostat Rating\u003c\/dt\u003e\n  \u003cdd\u003e140°F (60°C)\u003c\/dd\u003e\n  \u003cdt\u003eIncluded Kit Reference\u003c\/dt\u003e\n  \u003cdd\u003e18-3650\u003c\/dd\u003e\n  \u003cdt\u003eIncluded Thermostat Reference\u003c\/dt\u003e\n  \u003cdd\u003e18-3550\u003c\/dd\u003e\n  \u003cdt\u003eIncluded Gasket Reference\u003c\/dt\u003e\n  \u003cdd\u003e18-2831; gasket reference 27-47590-1\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n  \u003cdd\u003eReplacement service installation; confirm application and housing configuration before fitting\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cspan style=\"color:#d0021b;\"\u003e1 x\u003c\/span\u003e 140°F (60°C) thermostat\u003c\/li\u003e\n  \u003cli\u003e\n\u003cspan style=\"color:#d0021b;\"\u003e1 x\u003c\/span\u003e thermostat housing gasket\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eMake sure the engine is completely cool before beginning work. Follow the manufacturer’s service procedures and disconnect the battery where applicable.\u003c\/li\u003e\n  \u003cli\u003eDrain or collect coolant as required for the engine configuration and locate the thermostat housing.\u003c\/li\u003e\n  \u003cli\u003ePlace a suitable cloth or container beneath the housing to catch residual coolant, then remove the housing-cover fasteners.\u003c\/li\u003e\n  \u003cli\u003eRemove the old thermostat and gasket, noting the thermostat orientation before removal.\u003c\/li\u003e\n  \u003cli\u003eClean the housing and cover mating surfaces carefully. Remove old gasket material without damaging the sealing surfaces.\u003c\/li\u003e\n  \u003cli\u003eInstall the new thermostat in the same orientation as the original part and position the new gasket correctly.\u003c\/li\u003e\n  \u003cli\u003eReinstall the housing cover and tighten the fasteners to the engine manufacturer’s specified torque.\u003c\/li\u003e\n  \u003cli\u003eRestore the cooling system using the correct coolant or water configuration for the engine, then check the fluid level.\u003c\/li\u003e\n  \u003cli\u003eRun the engine according to the service manual and inspect the housing for leaks while monitoring operating temperature.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat does this kit include?\u003c\/summary\u003e\n  \u003cp\u003eIt includes one 140°F (60°C) thermostat and one thermostat housing gasket. The kit reference is 18-3650; the included component references are 18-3550 and 18-2831.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhich engines are listed for this kit?\u003c\/summary\u003e\n  \u003cp\u003eThe company application data lists MerCruiser 120 GM, 2.5L GM, 140 GM, 3.0L GM, 3.0L LX GM, and 165 GM applications, plus Chrysler Force 55, 60, and 65 HP applications. Confirm the exact engine and original part number before purchase.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eIs 140°F the correct temperature rating?\u003c\/summary\u003e\n  \u003cp\u003eThis kit is specified as a 140°F (60°C) thermostat. Use the temperature rating specified for your particular engine and verify it against the service manual before installation.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eMy model or serial number is not listed. Will it fit?\u003c\/summary\u003e\n  \u003cp\u003eFitment should not be determined from horsepower alone. Compare the engine brand, model, displacement, original thermostat, gasket, and applicable reference number with the information above or with the manufacturer’s service documentation.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eCan I reuse the old gasket?\u003c\/summary\u003e\n  \u003cp\u003eNo. A new gasket is included to provide a fresh seal during thermostat replacement. Reusing a compressed or damaged gasket can lead to leaks.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhy is the engine still overheating after replacement?\u003c\/summary\u003e\n  \u003cp\u003eContinued overheating can result from other cooling-system problems, including restricted passages, insufficient coolant flow, a damaged water pump or impeller where applicable, air in the system, or a faulty temperature-sensing component. Follow the engine manufacturer’s diagnostic procedures.\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 a replacement thermostat and gasket kit. The listed manufacturer and aftermarket reference numbers are provided for application identification; verify the exact brand and construction shown for the item supplied.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eShipping speed and cost\u003c\/summary\u003e\n  \u003cp\u003eAvailable shipping methods, delivery estimates, and costs are shown at checkout and may vary by destination.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWarranty and returns\u003c\/summary\u003e\n  \u003cp\u003eWarranty and return eligibility are subject to the seller’s current policy. Contact support with your order details if you need assistance.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003ch2\u003eSafety \u0026amp; Important Information\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify the engine model, displacement, horsepower, original part references, and thermostat orientation before ordering or installing.\u003c\/li\u003e\n  \u003cli\u003eDo not rely on a shared part number alone when engine model, year, serial range, or housing configuration differs.\u003c\/li\u003e\n  \u003cli\u003eWork only on a fully cooled engine and follow the applicable manufacturer service instructions.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended if you are not familiar with marine engine cooling systems.\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 Replacement Parts\u003c\/strong\u003e — We supply replacement components for common marine engine service applications.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eApplication-Focused Information\u003c\/strong\u003e — Reference numbers and fitment details are provided to help customers compare their original parts.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSupport When You Need It\u003c\/strong\u003e — Contact our team with your engine model and original part details when application guidance is needed.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50718266687803,"sku":"21TH004-G","price":29.7,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/21TH004-G_1_c1444464-ffb9-4be3-a7a3-8fc81dc25197.jpg?v=1762958560"}],"url":"https:\/\/seasierra.com\/collections\/mercury-mercruiser-4-stroke-120-165hp-outboard-marine-engine-parts.oembed","provider":"SeaSierra","version":"1.0","type":"link"}