{"product_id":"339-856991a1-339-850227-ignition-coil-for-mercury-efi-optimax-sport-jet-jlm-marine","title":"339-856991A1 339-850227 Ignition Coil for Mercury EFI Optimax Sport Jet | JLM Marine","description":"\u003ch2\u003eIgnition Coil for Mercury EFI Optimax Sport Jet – Fits 135-250 HP 6-Cylinder Engines\u003c\/h2\u003e\n\n\u003cp\u003eThis high-quality aftermarket ignition coil is engineered for Mercury EFI, Optimax, and Sport Jet outboard engines. Designed to fit 6-cylinder 2.5L and 3.0L models from 1998 to 2006, it delivers reliable spark performance for 135 HP to 250 HP applications.\u003c\/p\u003e\n\n\u003cp\u003eThis ignition coil directly replaces Mercury part numbers \u003cstrong\u003e339-856991A1\u003c\/strong\u003e, \u003cstrong\u003e339-850227\u003c\/strong\u003e, and Sierra part number \u003cstrong\u003e18-5187\u003c\/strong\u003e. It meets or exceeds OEM specifications for reliable engine operation.\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003eDirect-fit replacement for Mercury 6-cylinder EFI, Optimax, and Sport Jet engines\u003c\/li\u003e\n\u003cli\u003eMeets or exceeds OEM performance standards\u003c\/li\u003e\n\u003cli\u003ePackage includes one complete ignition coil assembly\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\u003eMercury\u003c\/td\u003e\n\u003ctd\u003e339-856991A1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003e339-850227\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSierra\u003c\/td\u003e\n\u003ctd\u003e18-5187\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 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\" target=\"_blank\" rel=\"nofollow noopener\"\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\" target=\"_blank\" rel=\"nofollow noopener\"\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\"\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\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eEFI\u003c\/td\u003e\n\u003ctd\u003e200\u003c\/td\u003e\n\u003ctd\u003e6 Cyl 2.5L\u003c\/td\u003e\n\u003ctd\u003e1998-2006\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eOptimax\u003c\/td\u003e\n\u003ctd\u003e135\u003c\/td\u003e\n\u003ctd\u003e6 Cyl 2.5L\u003c\/td\u003e\n\u003ctd\u003e1998-2006\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eOptimax\u003c\/td\u003e\n\u003ctd\u003e150\u003c\/td\u003e\n\u003ctd\u003e6 Cyl 2.5L\u003c\/td\u003e\n\u003ctd\u003e1998-2006\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eOptimax\u003c\/td\u003e\n\u003ctd\u003e175\u003c\/td\u003e\n\u003ctd\u003e6 Cyl 2.5L\u003c\/td\u003e\n\u003ctd\u003e2001-2006\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eEFI\u003c\/td\u003e\n\u003ctd\u003e225\u003c\/td\u003e\n\u003ctd\u003e6 Cyl 3.0L\u003c\/td\u003e\n\u003ctd\u003e1998-2006\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eSport Jet\u003c\/td\u003e\n\u003ctd\u003e250\u003c\/td\u003e\n\u003ctd\u003e6 Cyl 3.0L\u003c\/td\u003e\n\u003ctd\u003e2002-2006\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\u003eIgnition Coil\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApplication\u003c\/td\u003e\n\u003ctd\u003eMercury EFI, Optimax, Sport Jet Outboards\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEngine Configuration\u003c\/td\u003e\n\u003ctd\u003e6-Cylinder\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDisplacement\u003c\/td\u003e\n\u003ctd\u003e2.5L \/ 3.0L\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatible HP Range\u003c\/td\u003e\n\u003ctd\u003e135-250 HP\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eQuality Standard\u003c\/td\u003e\n\u003ctd\u003eMeets or exceeds OEM specifications\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;\"\u003e\u003cstrong\u003e1 x Ignition Coil\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 negative battery cable to prevent electrical shock or short circuits.\u003c\/li\u003e\n\u003cli\u003eLocate the ignition coil on your engine; refer to your engine's service manual or parts diagram for exact positioning.\u003c\/li\u003e\n\u003cli\u003eDisconnect the spark plug wire from the old ignition coil. Label wires if multiple coils are present.\u003c\/li\u003e\n\u003cli\u003eDisconnect the electrical connector from the ignition coil.\u003c\/li\u003e\n\u003cli\u003eRemove the mounting bolts or screws securing the old ignition coil to the engine block.\u003c\/li\u003e\n\u003cli\u003eCarefully lift the old ignition coil away from the engine.\u003c\/li\u003e\n\u003cli\u003ePosition the new ignition coil in the same location and align the mounting holes.\u003c\/li\u003e\n\u003cli\u003eSecure the new coil with the original mounting bolts or screws; tighten to manufacturer specifications.\u003c\/li\u003e\n\u003cli\u003eReconnect the electrical connector firmly until it clicks into place.\u003c\/li\u003e\n\u003cli\u003eAttach the spark plug wire to the new ignition coil, ensuring a secure connection.\u003c\/li\u003e\n\u003cli\u003eReconnect the negative battery cable.\u003c\/li\u003e\n\u003cli\u003eStart the engine and verify smooth operation with no misfires or rough idling.\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 ignition coil fits my engine?\u003c\/strong\u003e\u003cbr\u003e\nA: Check the Compatible Engine Models table above for your engine's brand, model, HP, and year range. You can also cross-reference the OEM part numbers (339-856991A1, 339-850227) with your original coil or consult your engine's parts diagram.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: What are the symptoms of a failing ignition coil?\u003c\/strong\u003e\u003cbr\u003e\nA: Common signs include engine misfires, rough idling, difficulty starting, loss of power under load, and increased fuel consumption. If your engine runs poorly on certain cylinders, the ignition coil may be faulty.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: How often should I replace my ignition coil?\u003c\/strong\u003e\u003cbr\u003e\nA: Ignition coils typically last several years under normal operating conditions. Replace them when you notice performance issues or during routine maintenance if they show signs of corrosion, cracking, or electrical failure.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: What is the difference between this aftermarket coil and the OEM version?\u003c\/strong\u003e\u003cbr\u003e\nA: This aftermarket ignition coil is manufactured to meet or exceed OEM specifications using comparable materials and design. It provides reliable performance at a more competitive price point compared to OEM parts.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Can I install this ignition coil myself?\u003c\/strong\u003e\u003cbr\u003e\nA: If you have basic mechanical skills and tools, installation is straightforward. However, professional installation is recommended to ensure proper fitment, electrical connections, and optimal engine performance.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Is this an OEM part 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":51981020725561,"sku":"24IC369","price":41.5,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/12_13867900-e3e8-4423-825c-bdcebc816a5d.jpg?v=1772414688","url":"https:\/\/jlmmarine.com\/es\/products\/339-856991a1-339-850227-ignition-coil-for-mercury-efi-optimax-sport-jet-jlm-marine","provider":"JLM Marine Boat Parts Limited","version":"1.0","type":"link"}