{"product_id":"8m2003959-oxygen-sensor-for-mercruiser-3-0l-4-3l-4-5l-5-0l-5-7l-6-2l-8-1l-8-2l-jlm-marine","title":"8M2003959 Oxygen Sensor for Mercruiser 3.0L 4.3L 4.5L 5.0L 5.7L 6.2L 8.1L 8.2L | JLM Marine","description":"\u003ch2\u003eOxygen Sensor for Mercruiser 3.0L 4.3L 4.5L 5.0L 5.7L 6.2L 8.1L 8.2L – OEM 8M2003959\u003c\/h2\u003e\n\n\u003cp\u003eThis aftermarket oxygen sensor is engineered to replace OEM part number \u003cstrong\u003e8M2003959\u003c\/strong\u003e for a wide range of Mercruiser sterndrive and inboard engines. It delivers reliable exhaust monitoring and fuel management across \u003cstrong\u003e3.0L, 4.3L, 4.5L, 5.0L, 5.7L, 6.2L, 8.1L, and 8.2L\u003c\/strong\u003e engine families, ensuring accurate air-fuel ratio feedback for optimal performance and emissions control.\u003c\/p\u003e\n\n\u003cp\u003eThis sensor directly replaces Mercruiser part numbers \u003cstrong\u003e710-8M2003959\u003c\/strong\u003e and \u003cstrong\u003e8M2003959\u003c\/strong\u003e, providing a cost-effective alternative to OEM components without sacrificing reliability or precision.\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003eDrop-in replacement for Mercruiser oxygen sensors on MPI and Mag series engines\u003c\/li\u003e\n\u003cli\u003eDesigned for sterndrive and inboard applications across multiple displacement ranges\u003c\/li\u003e\n\u003cli\u003eEnsures accurate exhaust gas monitoring for improved fuel economy and engine efficiency\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\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\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8M2003959\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e710-8M2003959\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.\u003c\/p\u003e\n\n\u003cdiv style=\"overflow-x:auto;\"\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003cth\u003eModel\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.1L INBOARD EC - 8.1L INBOARD (Base) EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.7\/6.2L MPI INBOARD EC - 5.7L MPI MIE EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e540 HP - 540\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 MAG \/ 8.2 MAG HO EC - 8.2L Mag EC (Base Model)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 MAG HO EC - 8.2L Mag EC (Base Model)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2L MAG \/ 8.2L MAG HO - 8.2L Mag (Base Model)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.0L, 350, 377 MAG MPI STERNDRIVE EC - 377 MAG MPI BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 HO EC - 8.2L INBOARD (H.O.) EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.7L MPI SKI EC - 5.7L SKI EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.0L, 350, 377 MAG MPI STERNDRIVE EC - 350 MAG MPI HORIZON ALPHA\/BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.0, 350, 377 MAG MPI STERNDRIVE EC - 350 MAG MPI HORIZON ALPHA\/BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.0, 350, 377 MAG MPI STERNDRIVE EC - 5.0L MPI ALPHA\/BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 HO EC - 8.2L INBOARD (BASE) EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 MAG HO EC - 8.2L Mag EC (H.O. Model)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003eVAZER 100 EC - 100 VAZER EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 MAG \/ 8.2 MAG HO EC - 8.2L Mag EC (H.O. Model)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e4.3L MPI ALPHA\/BRAVO EC - 4.3L MPI ALPHA\/BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.0L, 350, 377 MAG MPI STERNDRIVE EC - 5.0L MPI ALPHA\/BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 HORIZON \/ 8.2 HO EC - 8.2L INBOARD (H.O.) EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.1L INBOARD EC - 8.1L INBOARD (H.O.) EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003eSCORPION 350 EC \/ 377 HO EC - SCORPION 377 HO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003eSCORPION 350 EC \/ 377 HO EC - SCORPION 350 EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.0L, 350, 377 MAG MPI STERNDRIVE EC - 350 MAG MPI ALPHA\/BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e520 HP - 520\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.7\/6.2L MPI INBOARD EC - 6.2L MPI MIE EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2L MAG \/ 8.2L MAG HO - 8.2L Mag (H.O. Model)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e4.5L MPI ALPHA\/BRAVO - 4.5L MPI 250 Alpha\/Bravo EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e496 MAG STERNDRIVE EC - 496 MAG EC (H.O. Model)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e5.0, 350, 377 MAG MPI STERNDRIVE EC - 377 MAG MPI BRAVO EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e8.2 HORIZON \/ 8.2 HO EC - 8.2L INBOARD (Base) EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e3.0L MPI EC - 3.0L MPI EC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercruiser\u003c\/td\u003e\n\u003ctd\u003e496 MAG STERNDRIVE EC - 496 MAG EC (Base Model)\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\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\u003e8M2003959\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eOxygen Sensor\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApplication\u003c\/td\u003e\n\u003ctd\u003eMercruiser Sterndrive \u0026amp; Inboard Engines\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatible Engines\u003c\/td\u003e\n\u003ctd\u003e3.0L, 4.3L, 4.5L, 5.0L, 5.7L, 6.2L, 8.1L, 8.2L\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 × Oxygen Sensor (OEM 8M2003959)\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 shorts during installation.\u003c\/li\u003e\n\u003cli\u003eAllow the engine to cool completely before attempting to remove the old oxygen sensor.\u003c\/li\u003e\n\u003cli\u003eLocate the oxygen sensor on the exhaust manifold or exhaust system—refer to your engine's service manual for exact positioning.\u003c\/li\u003e\n\u003cli\u003eDisconnect the electrical connector from the old sensor by carefully releasing the locking tab.\u003c\/li\u003e\n\u003cli\u003eUsing an appropriate oxygen sensor socket or wrench, unthread the old sensor counterclockwise and remove it from the exhaust port.\u003c\/li\u003e\n\u003cli\u003eInspect the threads in the exhaust port for debris or damage; clean if necessary using a thread chaser or wire brush.\u003c\/li\u003e\n\u003cli\u003eApply a small amount of anti-seize compound to the threads of the new oxygen sensor (avoid getting compound on the sensor tip).\u003c\/li\u003e\n\u003cli\u003eHand-thread the new sensor into the exhaust port clockwise, then tighten to the manufacturer's specified torque (typically 30–40 ft-lbs).\u003c\/li\u003e\n\u003cli\u003eReconnect the electrical connector to the new sensor, ensuring it clicks securely into place.\u003c\/li\u003e\n\u003cli\u003eReconnect the negative battery cable and start the engine to verify proper operation.\u003c\/li\u003e\n\u003cli\u003eCheck for exhaust leaks around the sensor installation point and confirm that no warning lights appear on the instrument panel.\u003c\/li\u003e\n\u003cli\u003eTest-run the engine under normal operating conditions to ensure the sensor is providing accurate feedback to the ECM.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow do I confirm this oxygen sensor fits my Mercruiser engine?\u003c\/strong\u003e\u003cbr\u003e\nVerify your engine model and displacement against the compatibility table above. Cross-check the OEM part number \u003cstrong\u003e8M2003959\u003c\/strong\u003e in your service manual or parts diagram to ensure it matches your current sensor.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat are the signs that my oxygen sensor needs replacement?\u003c\/strong\u003e\u003cbr\u003e\nCommon symptoms include poor fuel economy, rough idling, sluggish acceleration, black exhaust smoke, or a Check Engine light. A failing sensor may also cause the engine to run too rich or too lean.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow often should I replace the oxygen sensor?\u003c\/strong\u003e\u003cbr\u003e\nOxygen sensors typically last 50,000–100,000 miles or 3–5 years, depending on operating conditions. Replace sooner if you notice performance issues or if the sensor is fouled by oil, coolant, or carbon buildup.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCan I use anti-seize on the sensor threads?\u003c\/strong\u003e\u003cbr\u003e\nYes, apply a light coat of high-temperature anti-seize to the threads (avoid the sensor tip). This prevents thread galling and makes future removal easier, especially in marine environments prone to corrosion.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWill this aftermarket sensor work the same as the OEM part?\u003c\/strong\u003e\u003cbr\u003e\nYes, this sensor is built to OEM specifications and provides the same voltage output and response time. It integrates seamlessly with your Mercruiser ECM for accurate air-fuel ratio control.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eOEM vs. Aftermarket?\u003c\/strong\u003e\u003cbr\u003e\nThis 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\u003eHow fast do you ship and how much does it cost?\u003c\/strong\u003e\u003cbr\u003e\nWe 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\u003eWhat is your warranty and return policy?\u003c\/strong\u003e\u003cbr\u003e\nThis 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":51981004276025,"sku":"23OS464","price":25.57,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/12_394118af-fbac-4943-9b34-0bf6ba01cc86.jpg?v=1772414345","url":"https:\/\/jlmmarine.com\/products\/8m2003959-oxygen-sensor-for-mercruiser-3-0l-4-3l-4-5l-5-0l-5-7l-6-2l-8-1l-8-2l-jlm-marine","provider":"JLM Marine Boat Parts Limited","version":"1.0","type":"link"}