{"product_id":"newhow-3-pack-ignition-coil-300-8m0077471-12v-for-mercury-optimax","title":"NEWHOW 3-Pack Ignition Coil 300-8M0077471 12V for Mercury Optimax","description":"\u003ch3\u003eKey features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e3-Pack 12V EFI\/DFI Smart Ignition Coils — Replaces 300-8M0077471 \/ 8M0077471 Set of three direct aftermarket ECM-driven ignition driver coils​ for Mercury\/Mariner OptiMax \u0026amp; EFI outboards. Each replaces Mercury 300-8M0077471, 8M0077471, 339-8M0077471​ and prior 879984T01, 879984T00, 879984A1, 339-879984T01\/T00\/A01, 300-879984T01, crossing Sierra 18-5158, CDI 184-0003, Recmar REC300-8M0077471. 12V, ~0.5-1.0Ω primary, ~5-15kΩ secondary, 20-40kV output, 2-pin plug + HT tower, epoxy black shell. Match old stamp 300-8M0077471 or 8M0077471​ before order.\u003c\/li\u003e\n\u003cli\u003eFor Mercury OptiMax DFI 75-250HP \u0026amp; EFI 30-60HP (2002-Up) Engineered for OptiMax 75\/80 Jet\/90\/115\/125 DFI 3-cyl, OptiMax 200\/225\/250 DFI 3.0L, EFI 4S 30\/40 3-cyl \u0026amp; 50\/60 4-cyl, 2.5L\/3.0L EFI 150-250, Pro XS 115-250, 225\/250 XS, 300 XS, MerCruiser SCi 600-1200 \/ QC4V race​ (S\/N 0T980000-Up on many OptiMax). 3 coils = complete set for 3-cyl OptiMax 75\/90\/115.\u003c\/li\u003e\n\u003cli\u003eFixes P0300 Misfire, OptiMax Beeper, Hard Start \u0026amp; Flat Spot Resolves smart-coil faults: ECM throws P0301-P0303 single-cyl misfire, OptiMax alarm beeps 3× at idle, cold start needs 5+ cranks, no power above 3500rpm on one cyl. Internal driver IGBT fails or secondary opens. New coil restores 20-40kV under ECM dwell. Test old: primary 0.5-1.0Ω across 2 pins, secondary 5-15kΩ pin-to-boot; open = dead.\u003c\/li\u003e\n\u003cli\u003eBolt to Head Coil Seat, Dielectric Grease on Plug Disconnect negative battery, unplug 2-pin, remove 1× 5mm bolt per coil, lift old coil off plug, seat new coil, torque 35 in-lb, reconnect plug, apply dielectric grease to HT tower before pushing boot on. Critical: OptiMax coils sit low on head — water intrusion kills them; reuse original boot or fit new OEM-style boot. Do not swap coil positions randomly on DFI (physical cyl mapping must stay).\u003c\/li\u003e\n\u003cli\u003eConfirm 2-Pin + HT Tower + EFI\/DFI Before Ordering This is the ECM-driven smart coil with 2-pin control plug + 1 HT tower​ for OptiMax DFI \u0026amp; EFI 4S\/2S engines (2002-Up). Before ordering, photo your old coil and confirm (1) two control pins, (2) one high-tension tower, (3) black epoxy housing, (4) stamp reads 300-8M0077471 or 8M0077471. Engine must be EFI\/DFI (OptiMax or EFI 4S\/2S)​ — carbureted models use a different ignition architecture and are not covered by this coil. If old coil has 4 pins or no HT tower, it is a different generation and will not fit.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eFree shipping on orders $50+. 30-day hassle-free returns.\u003c\/p\u003e","brand":"Belmont Warehouse","offers":[{"title":"Default Title","offer_id":43364224958673,"sku":"BW-B0DWS9RGX4","price":107.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/3123\/5793\/files\/51BBY-D0frL.jpg?v=1791317707","url":"https:\/\/belmontwarehouse.com\/products\/newhow-3-pack-ignition-coil-300-8m0077471-12v-for-mercury-optimax","provider":"Belmont Warehouse","version":"1.0","type":"link"}