{"product_id":"689-11181-00-cylinder-head-gasket-for-yamaha-mercury-mariner-c30-30a-w30-jlm-marine","title":"689-11181-00 Cylinder Head Gasket for Yamaha Mercury Mariner C30 30A W30 | JLM Marine","description":"\u003ch2\u003eCylinder Head Gasket – Fits Yamaha \u0026amp; Mercury Mariner 2-Stroke 25–30 HP Outboards\u003c\/h2\u003e\n\n\u003cp\u003eThis aftermarket cylinder head gasket is engineered for Yamaha and Mercury Mariner 2-stroke outboard engines rated at 25–30 HP. It is designed to fit models including Yamaha C30 and 30A, as well as Mercury Mariner 30A and W30 with 2-cylinder, single-carburetor configurations. Built to OEM specifications, this gasket ensures a reliable seal between the cylinder head and block, preventing combustion leaks and maintaining optimal engine performance.\u003c\/p\u003e\n\n\u003cp\u003eThis gasket directly replaces multiple OEM part numbers across Yamaha and Mercury Mariner systems, including Yamaha 689-11181-00 and Mercury 27-19138M. It offers broad compatibility with legacy part numbers, ensuring you can confidently service older or discontinued engine models without sourcing hard-to-find original components.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eDirect replacement for Yamaha 689-11181-00 and Mercury 27-19138M part numbers\u003c\/li\u003e\n  \u003cli\u003eDesigned for 2-stroke, 2-cylinder engines with single carburetor\u003c\/li\u003e\n  \u003cli\u003eEnsures proper compression and prevents coolant\/oil mixing\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Cross-Reference\u003c\/h2\u003e\n\n\u003cp\u003eUse this table to confirm equivalent part numbers across OEM and aftermarket brands.\u003c\/p\u003e\n\n\u003cdiv style=\"overflow-x:auto;\"\u003e\n\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\" style=\"border-collapse:collapse; width:100%;\"\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\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003e689-11181-00\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003e689-11181-A2-00\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003e689-11181-A1-00\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003e689-11181-A0-00\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003e689-11181-01-00\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003e689-11181-02-00\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eMercury Mariner\u003c\/td\u003e\n      \u003ctd\u003e27-19138M\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eMercury Mariner\u003c\/td\u003e\n      \u003ctd\u003e19138\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eMercury Mariner\u003c\/td\u003e\n      \u003ctd\u003e27-84733M\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eSierra\u003c\/td\u003e\n      \u003ctd\u003e18-3804\u003c\/td\u003e\n    \u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eCompatible Engine Models\u003c\/h2\u003e\n\n\u003cp\u003eConfirm your engine model\/year in the table below. For Yamaha owners, here's a guide to help you identify your engine's serial\/model: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/serial-number-guide\/yamaha-outboard-serial-number-guide-2025\" rel=\"nofollow noopener\" target=\"_blank\"\u003eYamaha Serial Number Guide\u003c\/a\u003e. You can also review exploded diagrams to verify part numbers: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/serial-number-guide\/yamaha-outboard-parts-diagrams-catalog\" rel=\"nofollow noopener\" target=\"_blank\"\u003eYamaha Parts Diagrams \u0026amp; Catalog\u003c\/a\u003e.\u003c\/p\u003e\n\n\u003cp\u003eFor Mercury owners, here's a guide to help you identify your engine's serial\/model: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/serial-number-guide\/mercury-outboard-serial-number-guide\" rel=\"nofollow noopener\" target=\"_blank\"\u003eMercury Serial Number Guide\u003c\/a\u003e. You can also review exploded diagrams to verify part numbers: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/diagrams\/mercury-parts-catalog\" rel=\"nofollow noopener\" target=\"_blank\"\u003eMercury Parts Diagrams \u0026amp; Catalog\u003c\/a\u003e.\u003c\/p\u003e\n\n\u003cdiv style=\"overflow-x:auto;\"\u003e\n\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\" style=\"border-collapse:collapse; width:100%;\"\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\u003eNotes\u003c\/th\u003e\n    \u003c\/tr\u003e\n  \u003c\/thead\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003eC30\u003c\/td\u003e\n      \u003ctd\u003e25–30 HP\u003c\/td\u003e\n      \u003ctd\u003e2-Stroke\u003c\/td\u003e\n      \u003ctd\u003e2-cylinder, single carburetor, S\/N 689...\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003e30A\u003c\/td\u003e\n      \u003ctd\u003e30 HP\u003c\/td\u003e\n      \u003ctd\u003e2-Stroke\u003c\/td\u003e\n      \u003ctd\u003e2-cylinder, single carburetor, S\/N 689...\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eYamaha\u003c\/td\u003e\n      \u003ctd\u003eW30\u003c\/td\u003e\n      \u003ctd\u003e30 HP\u003c\/td\u003e\n      \u003ctd\u003e2-Stroke\u003c\/td\u003e\n      \u003ctd\u003e2-cylinder, single carburetor, S\/N 689...\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eMercury Mariner\u003c\/td\u003e\n      \u003ctd\u003e30A\u003c\/td\u003e\n      \u003ctd\u003e30 HP\u003c\/td\u003e\n      \u003ctd\u003e2-Stroke\u003c\/td\u003e\n      \u003ctd\u003e2-cylinder, single carburetor, Japan models, S\/N 689...\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eMercury Mariner\u003c\/td\u003e\n      \u003ctd\u003eW30\u003c\/td\u003e\n      \u003ctd\u003e30 HP\u003c\/td\u003e\n      \u003ctd\u003e2-Stroke\u003c\/td\u003e\n      \u003ctd\u003e2-cylinder, single carburetor, Japan models, S\/N 689...\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\n\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\" style=\"border-collapse:collapse; width:100%;\"\u003e\n  \u003cthead\u003e\n    \u003ctr\u003e\n      \u003cth\u003eSpecification\u003c\/th\u003e\n      \u003cth\u003eValue\u003c\/th\u003e\n    \u003c\/tr\u003e\n  \u003c\/thead\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n      \u003ctd\u003ePart Type\u003c\/td\u003e\n      \u003ctd\u003eCylinder Head Gasket\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eApplication\u003c\/td\u003e\n      \u003ctd\u003eYamaha \u0026amp; Mercury Mariner 2-Stroke Outboards\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eEngine Configuration\u003c\/td\u003e\n      \u003ctd\u003e2-Cylinder, Single Carburetor\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eHorsepower Range\u003c\/td\u003e\n      \u003ctd\u003e25–30 HP\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eStroke Type\u003c\/td\u003e\n      \u003ctd\u003e2-Stroke\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eOEM Reference\u003c\/td\u003e\n      \u003ctd\u003e689-11181-00\u003c\/td\u003e\n    \u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003ePackage Contents\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\u003cspan style=\"color:red;\"\u003e1 × Outboard Cylinder Head Gasket\u003c\/span\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Guide\u003c\/h2\u003e\n\n\u003col\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDisconnect the battery\u003c\/strong\u003e and allow the engine to cool completely before beginning work.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRemove the engine cowling\u003c\/strong\u003e and label all electrical connections for easy reassembly.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDetach fuel lines and control cables\u003c\/strong\u003e from the cylinder head area. Cap open fuel lines to prevent spills.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUnbolt and lift off the cylinder head\u003c\/strong\u003e carefully, noting the positions of all fasteners.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRemove the old gasket\u003c\/strong\u003e and thoroughly clean both the cylinder head and block mating surfaces. Use a gasket scraper and solvent; ensure no residue or debris remains.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInspect the cylinder head for warping or cracks\u003c\/strong\u003e using a straight edge. Replace or resurface if necessary.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePosition the new gasket\u003c\/strong\u003e on the block, aligning all bolt holes and coolant passages precisely.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReinstall the cylinder head\u003c\/strong\u003e and hand-tighten all bolts to ensure proper seating.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eTorque the head bolts\u003c\/strong\u003e in a cross-pattern sequence to manufacturer specifications (consult your service manual).\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReconnect fuel lines, control cables, and electrical connections\u003c\/strong\u003e in reverse order of removal.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRefill coolant\u003c\/strong\u003e (if applicable) and check for leaks before starting the engine.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eStart the engine and inspect\u003c\/strong\u003e for proper compression, coolant leaks, and smooth operation. Re-torque head bolts after initial run-in if recommended.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: How do I confirm this gasket fits my engine?\u003c\/strong\u003e\u003cbr\u003e\nA: Cross-reference your engine's model number and serial number with the compatibility table above. Verify that your engine is a 2-stroke, 2-cylinder configuration with a single carburetor and matches the listed HP range (25–30 HP).\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: What are the signs that my cylinder head gasket needs replacement?\u003c\/strong\u003e\u003cbr\u003e\nA: Common symptoms include loss of compression, overheating, white smoke from the exhaust, coolant mixing with oil, external coolant or oil leaks near the head, and rough idling or misfires.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Can I reuse the old gasket if it looks intact?\u003c\/strong\u003e\u003cbr\u003e\nA: No. Cylinder head gaskets are designed for single use. Reusing an old gasket—even if it appears undamaged—can result in improper sealing, leaks, and engine damage.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Do I need to resurface the cylinder head before installing this gasket?\u003c\/strong\u003e\u003cbr\u003e\nA: Inspect the cylinder head with a straight edge. If warping or damage is present, resurfacing is required. Clean, flat mating surfaces are essential for a proper seal.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: How often should I replace the cylinder head gasket?\u003c\/strong\u003e\u003cbr\u003e\nA: Replace the gasket any time the cylinder head is removed for service, repair, or inspection. Regular replacement intervals are not specified, but symptoms of failure (overheating, leaks, compression loss) indicate immediate replacement is needed.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Is this an OEM or aftermarket part?\u003c\/strong\u003e\u003cbr\u003e\nA: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: How fast do you ship and how much does it cost?\u003c\/strong\u003e\u003cbr\u003e\nA: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: What is your warranty and return policy?\u003c\/strong\u003e\u003cbr\u003e\nA: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused \u0026amp; in original condition); please see our policy page or reach out for instructions.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Notes\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003eVerify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.\u003c\/li\u003e\n  \u003cli\u003eThis product is an aftermarket replacement part and is not an OEM component.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended to ensure safety and optimal performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose JLM MARINE?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eQuality Assured:\u003c\/strong\u003e As a trusted manufacturer for over 20 years, we supply top marine brands globally.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFast Global Shipping:\u003c\/strong\u003e Free delivery worldwide in 5–15 days.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDirect from Manufacturer:\u003c\/strong\u003e Competitive pricing without compromising quality.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"JLM Marine","offers":[{"title":"Default Title","offer_id":51981000245561,"sku":"23GT285","price":22.5,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/12_a3c9b19f-0e1a-4627-8392-bc48d3a796e8.jpg?v=1772414152","url":"https:\/\/jlmmarine.com\/es\/products\/689-11181-00-cylinder-head-gasket-for-yamaha-mercury-mariner-c30-30a-w30-jlm-marine","provider":"JLM Marine Boat Parts Limited","version":"1.0","type":"link"}