{"product_id":"6h4-11181-00-cylinder-head-gasket-for-yamaha-40hp-50hp-pro-50-jlm-marine","title":"6H4-11181-00 Cylinder Head Gasket for Yamaha 40HP 50HP Pro 50 | JLM Marine","description":"\u003cbody\u003e\n\n\n\u003cmeta charset=\"UTF-8\"\u003e\n\n\n\n\u003ch2\u003eCylinder Head Gasket for Yamaha 40HP 50HP Pro 50 Outboard Engines\u003c\/h2\u003e\n\n\u003cp\u003eThis cylinder head gasket is designed to fit \u003cstrong\u003eYamaha 40HP and 50HP (including Pro 50) 2-stroke outboard engines\u003c\/strong\u003e manufactured between 1984 and 1994. It provides a reliable seal between the cylinder head and engine block, preventing compression loss and coolant leaks.\u003c\/p\u003e\n\n\u003cp\u003eThis aftermarket replacement directly replaces Yamaha OEM part numbers \u003cstrong\u003e6H4-11181-00\u003c\/strong\u003e, 6H4-11181-A0-00, 6H4-11181-A1-00, 6H4-11181-A2-00, 6H4-11181-01-00, and Sierra part number \u003cstrong\u003e18-3830\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003ePrecision-cut design ensures proper compression sealing\u003c\/li\u003e\n\u003cli\u003eCompatible with Yamaha 2-stroke 40HP and 50HP models from 1984-1994\u003c\/li\u003e\n\u003cli\u003eDirect fit replacement for multiple OEM part numbers\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\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\"\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\u003e6H4-11181-00\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003e6H4-11181-A0-00\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003e6H4-11181-A1-00\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003e6H4-11181-A2-00\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003e6H4-11181-01-00\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSierra\u003c\/td\u003e\n\u003ctd\u003e18-3830\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\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\u003cdiv style=\"overflow-x:auto;\"\u003e\n\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\"\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\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003e40\u003c\/td\u003e\n\u003ctd\u003e40 HP\u003c\/td\u003e\n\u003ctd\u003e2-Stroke\u003c\/td\u003e\n\u003ctd\u003e1984-1994\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003e50\u003c\/td\u003e\n\u003ctd\u003e50 HP\u003c\/td\u003e\n\u003ctd\u003e2-Stroke\u003c\/td\u003e\n\u003ctd\u003e1984-1994\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003ePro 50\u003c\/td\u003e\n\u003ctd\u003e50 HP\u003c\/td\u003e\n\u003ctd\u003e2-Stroke\u003c\/td\u003e\n\u003ctd\u003e1984-1994\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\"\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\u003eOEM Part Number\u003c\/td\u003e\n\u003ctd\u003e6H4-11181-00\u003c\/td\u003e\n\u003c\/tr\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\u003eEngine Type\u003c\/td\u003e\n\u003ctd\u003e2-Stroke Outboard\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eHorsepower Range\u003c\/td\u003e\n\u003ctd\u003e40HP - 50HP\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFitment Years\u003c\/td\u003e\n\u003ctd\u003e1984-1994\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\u003cp\u003eThis package includes the following component:\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003e\u003cspan style=\"color:red;\"\u003e\u003cstrong\u003e1 × Outboard Cylinder Head Gasket\u003c\/strong\u003e\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\u003ePreparation:\u003c\/strong\u003e Disconnect the battery and allow the engine to cool completely. Gather necessary tools including a torque wrench, gasket scraper, and cleaning solvent.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove Cylinder Head:\u003c\/strong\u003e Disconnect fuel lines, spark plug wires, and coolant hoses from the cylinder head. Remove the cylinder head bolts in a crisscross pattern, working from outside toward the center.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eClean Surfaces:\u003c\/strong\u003e Carefully remove the old gasket material from both the cylinder head and engine block using a gasket scraper. Ensure all surfaces are completely clean and free of debris or oil residue.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInspect Components:\u003c\/strong\u003e Check the cylinder head and block for warping, cracks, or damage. Replace any damaged components before proceeding.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePosition New Gasket:\u003c\/strong\u003e Place the new cylinder head gasket onto the engine block, ensuring all bolt holes and coolant passages align correctly. Do not apply any sealant unless specified by the manufacturer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall Cylinder Head:\u003c\/strong\u003e Carefully lower the cylinder head onto the gasket, ensuring proper alignment. Hand-thread all bolts before tightening.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTorque Bolts:\u003c\/strong\u003e Tighten the cylinder head bolts in a crisscross pattern, working from the center outward. Follow the manufacturer's torque specifications and sequence for your specific engine model.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReconnect Components:\u003c\/strong\u003e Reattach all fuel lines, spark plug wires, and coolant hoses. Double-check all connections for security.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRefill Fluids:\u003c\/strong\u003e Add fresh coolant to the system and check oil levels. Bleed air from the cooling system according to your engine's service manual.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest Engine:\u003c\/strong\u003e Reconnect the battery and start the engine. Check for leaks around the cylinder head gasket while the engine warms up.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRe-torque:\u003c\/strong\u003e After the first few hours of operation, re-check and re-torque the cylinder head bolts to specification. This ensures proper seating of the gasket.\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 Yamaha engine?\u003c\/strong\u003e\u003cbr\u003e\nA: Verify your engine is a Yamaha 40HP or 50HP (including Pro 50) 2-stroke model manufactured between 1984 and 1994. Cross-reference your original part number (6H4-11181-00 or equivalents listed above) with our compatibility table.\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, coolant leaks around the cylinder head, white smoke from the exhaust, rough idle, and coolant mixing with engine oil.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Can I reuse the old cylinder head bolts during installation?\u003c\/strong\u003e\u003cbr\u003e\nA: It's recommended to replace cylinder head bolts, especially if they are torque-to-yield (TTY) type. Consult your engine's service manual to determine if bolt replacement is required for proper clamping force.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Do I need to use sealant with this gasket?\u003c\/strong\u003e\u003cbr\u003e\nA: Most cylinder head gaskets are designed to be installed dry without additional sealant. Consult your Yamaha service manual for specific instructions regarding your engine model.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: How often should I replace the cylinder head gasket?\u003c\/strong\u003e\u003cbr\u003e\nA: Cylinder head gaskets should be replaced only when symptoms of failure appear or during major engine rebuilds. With proper maintenance and cooling system care, a quality gasket can last for many years.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: What's the difference between OEM and aftermarket gaskets?\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\n\n\n\u003c\/body\u003e","brand":"JLM Marine","offers":[{"title":"Default Title","offer_id":51981000376633,"sku":"23GT291","price":20.42,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/12_d51ba465-736c-49b3-8455-29ff9d29d9ee.jpg?v=1772414162","url":"https:\/\/jlmmarine.com\/products\/6h4-11181-00-cylinder-head-gasket-for-yamaha-40hp-50hp-pro-50-jlm-marine","provider":"JLM Marine Boat Parts Limited","version":"1.0","type":"link"}