{"product_id":"merc-47","title":"Mercury Quicksilver 18785T Cylinder Head Gasket — V-135 \/ V-150 V6 Outboard","description":"\u003csection class=\"product-description\"\u003e\n\n\u003ch2\u003eMercury Quicksilver 18785T — Cylinder Head Gasket, V-135 \/ V-150 V6 Outboard\u003c\/h2\u003e\n\n\u003ctable\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003ePart Number\u003c\/th\u003e\n\u003ctd\u003e18785T\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eService Format\u003c\/th\u003e\n\u003ctd\u003e27-18785T\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eSKU\u003c\/th\u003e\n\u003ctd\u003e18785T\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003ctd\u003eMercury \/ Quicksilver (OEM)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eProduct Type\u003c\/th\u003e\n\u003ctd\u003eCylinder Head Gasket\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eSystem\u003c\/th\u003e\n\u003ctd\u003eMercury V6 Outboard Powerhead — Cylinder Head Sealing\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eSupersedes\u003c\/th\u003e\n\u003ctd\u003e187851 \/ 187853\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eGTIN\u003c\/th\u003e\n\u003ctd\u003e745061124424\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eWeight\u003c\/th\u003e\n\u003ctd\u003eapprox. 100 g\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eThe Mercury Quicksilver 18785T is a genuine OEM cylinder head gasket for selected Mercury V6 outboard powerheads. It seals the joint between the cylinder head and powerhead block, maintaining combustion pressure and preventing coolant or water intrusion into the combustion chamber. Mercury parts diagrams place 18785T directly at the cylinder head \/ block interface in V-135 and V-150 V6 applications within the specified serial ranges.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eImportant:\u003c\/strong\u003e Head gaskets are highly application-specific. Combustion-ring diameter, coolant passage layout, thickness, and sealing pattern must all match the exact block and cylinder-head combination. A gasket that looks similar can cause compression loss or cooling problems if it is not the correct part for that specific powerhead. Always confirm by exact model and serial number before ordering.\u003c\/p\u003e\n\n\u003ch2\u003eSupersession\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCurrent part number:\u003c\/strong\u003e 18785T (service format: 27-18785T)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSupersedes:\u003c\/strong\u003e 187851\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSupersedes:\u003c\/strong\u003e 187853\u003c\/li\u003e\n  \u003cli\u003eIf your service records or parts diagram show 187851 or 187853, 18785T is the correct current OEM replacement.\u003c\/li\u003e\n  \u003cli\u003eRelated V6 head gasket variants include \u003cstrong\u003e18786T\u003c\/strong\u003e and \u003cstrong\u003e822844T05\u003c\/strong\u003e — these apply to different XR, Magnum, EFI, or Jet configurations within the same engine family. Confirm by exact model and serial number before substituting.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatible Applications\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eMercury V-135 — serial range 0C239553–0G960499\u003c\/li\u003e\n  \u003cli\u003eMercury V-135 — serial range 0G960500–0T178499\u003c\/li\u003e\n  \u003cli\u003eMercury V-150 — serial range 0C239553–0G960499\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAlways confirm by exact model and serial number\u003c\/strong\u003e — related Mercury V6 engines (XR, Magnum, EFI, Jet variants) can use different head gaskets depending on configuration\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen to Replace\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eAny time the cylinder head is removed — head gaskets should never be reused once the head has been lifted\u003c\/li\u003e\n  \u003cli\u003eSigns of combustion gas leakage at the head\/block joint (bubbles in the cooling system, white exhaust smoke)\u003c\/li\u003e\n  \u003cli\u003eWater or coolant intrusion into the combustion chamber\u003c\/li\u003e\n  \u003cli\u003eCompression loss traced to the head gasket rather than rings or valves\u003c\/li\u003e\n  \u003cli\u003eVisible gasket deterioration, erosion at coolant passages, or blown combustion ring\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eDo not reuse the original head gasket — replace with a new OEM gasket every time the cylinder head is removed\u003c\/li\u003e\n  \u003cli\u003eThoroughly clean both the cylinder-head and block mating surfaces before installation — gasket residue, corrosion, or debris will cause leaks\u003c\/li\u003e\n  \u003cli\u003eInspect both mating surfaces for warping, erosion, or corrosion pitting; a distorted head or block surface must be machined flat before a new gasket will seal reliably\u003c\/li\u003e\n  \u003cli\u003eInstall the gasket in the correct orientation as shown in the Mercury service manual for the exact model and serial range\u003c\/li\u003e\n  \u003cli\u003eTighten cylinder-head fasteners in the specified sequence and in torque stages per the Mercury service manual — incorrect torque sequence is one of the most common causes of head gasket failure on reinstallation\u003c\/li\u003e\n  \u003cli\u003eReplace all head fasteners if the service manual specifies torque-to-yield bolts (one-time use)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical FAQ\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCan I reuse my original head gasket if it looks undamaged?\u003c\/strong\u003e No. Head gaskets deform under clamping load during initial installation and will not seal reliably if reused. Always install a new OEM gasket whenever the cylinder head is removed.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWhat is the difference between 18785T, 18786T, and 822844T05?\u003c\/strong\u003e These are different head gaskets within the Mercury V6 outboard engine family, used on different configurations (XR, Magnum, EFI, Jet) and serial ranges. They are not interchangeable — confirm the exact correct part number using your model and serial number in the Mercury parts catalog before ordering.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMy engine is overheating after a head gasket replacement — what should I check?\u003c\/strong\u003e Verify that the head was not warped — a distorted mating surface will cause a new gasket to fail immediately. Also confirm all coolant passages were clear of debris before reassembly, and that the head fasteners were torqued in the correct sequence and to the correct specification.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHow do I know if my head gasket has failed without disassembly?\u003c\/strong\u003e Common signs include white smoke from the exhaust, unexplained coolant loss, bubbles in the cooling system reservoir, compression loss in one or more cylinders, or oil\/water contamination. A cylinder leakdown or compression test can help confirm head gasket failure before disassembly.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eParts Desk Insights\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eBest Use Case:\u003c\/strong\u003e This gasket is the correct choice for a cylinder head service on Mercury V-135 or V-150 V6 outboards within the confirmed serial ranges. The most common scenario is during a powerhead rebuild, overheating repair, or whenever the cylinder head has been removed for inspection or service. Because head gaskets must never be reused once the head is lifted, ordering the replacement gasket before teardown is standard practice.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCommon Issues:\u003c\/strong\u003e The most frequent problem is ordering a head gasket by engine displacement alone without confirming the exact model variant and serial range. The Mercury V6 outboard family includes XR, Magnum, EFI, and Jet configurations that use different head gaskets — including 18786T and 822844T05 — that are not interchangeable with 18785T. The second common issue is head gasket failure after reinstallation due to a warped mating surface that was not inspected or machined before reassembly. A new gasket on a distorted surface will not hold.\u003c\/p\u003e\n\n\u003ch2\u003eRelated Products\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003ca href=\"https:\/\/marisolmarine.com\/products\/mercury-high-performance-2-stroke-oil-8m0078011\"\u003eMercury High Performance 2-Stroke Oil — 8M0078011\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/section\u003e","brand":"MERC","offers":[{"title":"Default Title","offer_id":43563839619108,"sku":"18785T","price":104.45,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0743\/5799\/7604\/files\/d26b1836-0525-4aa2-8a27-8c8ca42b03c6.png?v=1786479761","url":"https:\/\/marisolmarine.com\/products\/merc-47","provider":"Marisol Marine Company","version":"1.0","type":"link"}