{"product_id":"329103-head-gasket-for-johnson-evinrude-omc-5hp-5-5hp-6hp-jlm-marine","title":"329103 Head Gasket for Johnson Evinrude OMC 5HP 5.5HP 6HP | JLM Marine","description":"\u003ch2\u003eHead Gasket for Johnson Evinrude OMC 5HP 5.5HP 6HP\u003c\/h2\u003e\n\n\u003cp\u003eThis cylinder head gasket is designed for Johnson Evinrude OMC outboard engines rated at \u003cstrong\u003e5HP, 5.5HP, and 6HP\u003c\/strong\u003e. It provides a reliable seal between the cylinder head and engine block, ensuring optimal compression and preventing coolant or combustion gas leaks.\u003c\/p\u003e\n\n\u003cp\u003eThis aftermarket replacement directly replaces OEM part numbers \u003cstrong\u003e306204, 329103, and 777397\u003c\/strong\u003e, as well as GLM 33830 and Sierra 18-2961, offering broad compatibility across multiple model years from 1959 through 1979.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eFits Johnson Evinrude OMC 5HP (1965-68), 5.5HP (1959-64), and 6HP (1965-79) outboards\u003c\/li\u003e\n  \u003cli\u003eDirect replacement for multiple OEM and aftermarket part numbers\u003c\/li\u003e\n  \u003cli\u003eSingle gasket included per package\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\u003eJohnson Evinrude OMC\u003c\/td\u003e\n      \u003ctd\u003e306204\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eJohnson Evinrude OMC\u003c\/td\u003e\n      \u003ctd\u003e329103\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eJohnson Evinrude OMC\u003c\/td\u003e\n      \u003ctd\u003e777397\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eGLM\u003c\/td\u003e\n      \u003ctd\u003e33830\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eSierra\u003c\/td\u003e\n      \u003ctd\u003e18-2961\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 Johnson\/Evinrude owners, here's a guide to help you identify your engine's serial\/model: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/serial-number-guide\/johnson-serial-number-guide\" rel=\"nofollow noopener\" target=\"_blank\"\u003eJohnson Serial Number Guide\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\u003eRated HP\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\u003eEvinrude Johnson OMC\u003c\/td\u003e\n        \u003ctd\u003e5 HP\u003c\/td\u003e\n        \u003ctd\u003e1965-68\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eEvinrude Johnson OMC\u003c\/td\u003e\n        \u003ctd\u003e5.5 HP\u003c\/td\u003e\n        \u003ctd\u003e1959-64\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eEvinrude Johnson OMC\u003c\/td\u003e\n        \u003ctd\u003e6 HP\u003c\/td\u003e\n        \u003ctd\u003e1965-79\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\u003ePart Type\u003c\/td\u003e\n      \u003ctd\u003eCylinder Head Gasket\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eCompatible Brand\u003c\/td\u003e\n      \u003ctd\u003eJohnson Evinrude OMC\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eCompatible HP Range\u003c\/td\u003e\n      \u003ctd\u003e5HP, 5.5HP, 6HP\u003c\/td\u003e\n    \u003c\/tr\u003e\n    \u003ctr\u003e\n      \u003ctd\u003eOEM Part Number\u003c\/td\u003e\n      \u003ctd\u003e329103\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\u003eEach package includes:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\u003cspan style=\"color:red;\"\u003e\u003cstrong\u003e1 × 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\u003eDisconnect the spark plug wire to prevent accidental starting during service.\u003c\/li\u003e\n  \u003cli\u003eRemove the cylinder head bolts in a crisscross pattern to avoid warping the head.\u003c\/li\u003e\n  \u003cli\u003eCarefully lift off the cylinder head and set it on a clean work surface.\u003c\/li\u003e\n  \u003cli\u003eThoroughly clean both the cylinder head and engine block mating surfaces, removing all traces of the old gasket material and carbon deposits.\u003c\/li\u003e\n  \u003cli\u003eInspect the cylinder head for cracks, warping, or damage; resurface or replace if necessary.\u003c\/li\u003e\n  \u003cli\u003ePosition the new head gasket on the engine block, ensuring all bolt holes and coolant passages align correctly.\u003c\/li\u003e\n  \u003cli\u003eCarefully lower the cylinder head onto the gasket, avoiding any shifting that could damage the seal.\u003c\/li\u003e\n  \u003cli\u003eHand-thread all cylinder head bolts to prevent cross-threading.\u003c\/li\u003e\n  \u003cli\u003eTorque the head bolts to the manufacturer's specification in a crisscross sequence, working from the center outward.\u003c\/li\u003e\n  \u003cli\u003eReconnect the spark plug wire and any other components removed during disassembly.\u003c\/li\u003e\n  \u003cli\u003eStart the engine and check for leaks around the head gasket area.\u003c\/li\u003e\n  \u003cli\u003eAllow the engine to reach operating temperature, then recheck torque specifications after the first few hours of use.\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 specific Johnson or Evinrude engine?\u003c\/strong\u003e\u003cbr\u003e\nA: Cross-reference your engine's HP rating and year with the compatibility table above. This gasket fits 5HP (1965-68), 5.5HP (1959-64), and 6HP (1965-79) models. You can also verify by matching your original OEM part number (306204, 329103, or 777397) with those listed.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: How often should I replace the cylinder head gasket?\u003c\/strong\u003e\u003cbr\u003e\nA: Head gaskets should be replaced whenever the cylinder head is removed for service, or immediately if you notice compression loss, coolant leaks, or overheating. Regular maintenance intervals vary, but inspect annually for engines used frequently.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: What are the signs that my head gasket is failing?\u003c\/strong\u003e\u003cbr\u003e\nA: Common symptoms include overheating, loss of power, visible coolant leaks around the cylinder head, white smoke from the exhaust, or oil contamination in the cooling system. If you observe any of these, inspect and replace the gasket promptly.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Do I need to apply sealant to this gasket during installation?\u003c\/strong\u003e\u003cbr\u003e\nA: Most modern head gaskets are designed to seal without additional sealant. Check your engine's service manual for specific recommendations. Over-application of sealant can actually cause sealing issues or block coolant passages.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Is this OEM or aftermarket?\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":51981000835385,"sku":"23GT338","price":17.57,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/1_c3c4231c-e819-4af8-ae7c-1c51245588e4.png?v=1772414201","url":"https:\/\/jlmmarine.com\/products\/329103-head-gasket-for-johnson-evinrude-omc-5hp-5-5hp-6hp-jlm-marine","provider":"JLM Marine Boat Parts Limited","version":"1.0","type":"link"}