{"product_id":"ifjf-18-7817-fuel-pump-kit-diaphragm-washer-kit-for-mercury-mariner-outboard-21-857005a1-1","title":"18-7817 Fuel Pump Diaphragm Kit for Mercury Mariner Outboard","description":"\u003ch2\u003eFuel Pump Diaphragm \u0026amp; Washer Kit for Mercury\/Mariner Outboard\u003c\/h2\u003e\n\u003cp\u003eThe iFJF 18-7817 fuel pump rebuild kit restores proper fuel delivery for your Mercury or Mariner outboard engine. This kit replaces the critical diaphragm and check valves inside the mechanical pulse-style fuel pump — the components most prone to wear and ethanol-related deterioration. Replaces Mercury OEM 21-857005A1 and Sierra Marine 18-7817.\u003c\/p\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete Rebuild Kit:\u003c\/strong\u003e Includes fuel pump diaphragm, check valves, gaskets, and washers — everything needed to restore a mechanical pulse fuel pump.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEthanol-Ready Diaphragm:\u003c\/strong\u003e Upgraded elastomer material resists stiffening, cracking, and perforation caused by ethanol-blended fuels.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRestores Fuel Pressure:\u003c\/strong\u003e Fixes weak fuel delivery, hard starting after sitting, and engine stalling under load caused by a failing diaphragm.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDirect OEM Replacement:\u003c\/strong\u003e Manufactured to match Mercury\/Mariner OEM specifications for pulse pump dimensions and flow rates.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCost-Saving Alternative:\u003c\/strong\u003e A complete OEM fuel pump assembly costs $80-150+. This rebuild kit achieves the same result at a fraction of the cost.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCross-Reference \/ Interchange\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003cth\u003ePart Number\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSierra Marine\u003c\/td\u003e\n\u003ctd\u003e18-7817\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury \/ Mariner OEM\u003c\/td\u003e\n\u003ctd\u003e21-857005A1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eSigns of a Failing Fuel Pump Diaphragm\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHard starting after sitting:\u003c\/strong\u003e Fuel drains back to the tank overnight — requires excessive cranking to re-prime.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEngine stalls under load:\u003c\/strong\u003e Pump can't maintain fuel volume at higher RPM\/load demands.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFuel in the pulse line:\u003c\/strong\u003e A perforated diaphragm allows fuel to enter the crankcase pulse line (dangerous — can dilute engine oil).\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSurging at cruise speed:\u003c\/strong\u003e Inconsistent fuel pressure causes RPM fluctuations.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVisible cracking on diaphragm:\u003c\/strong\u003e Upon inspection, the rubber is stiff, cracked, or has pinholes.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Does this kit fit all Mercury\/Mariner outboards?\u003c\/strong\u003e\u003cbr\u003eA: This kit is designed for mechanical pulse-style fuel pumps found on many Mercury\/Mariner 2-stroke outboards. Verify your pump matches OEM number 21-857005A1 before ordering. Not compatible with electric fuel pump systems.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Can I rebuild the pump without removing it from the engine?\u003c\/strong\u003e\u003cbr\u003eA: It's possible but not recommended. The pump is typically held by 2 bolts and the fuel lines. Removing it allows you to clean the mating surfaces properly and inspect the pulse port for blockages.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: What tools are needed?\u003c\/strong\u003e\u003cbr\u003eA: Basic hand tools — Phillips screwdriver, flathead for prying, and a socket or wrench for the mounting bolts (typically 10mm or 3\/8\"). A pick tool helps remove old gasket material.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: How often should I rebuild the fuel pump?\u003c\/strong\u003e\u003cbr\u003eA: As preventative maintenance, every 3-5 years if using ethanol fuel, or when symptoms of failure appear. If you run ethanol-free marine fuel, the diaphragm can last 8-10+ years.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Is this kit compatible with fuel-injected outboards?\u003c\/strong\u003e\u003cbr\u003eA: No. Fuel-injected outboards use high-pressure electric pumps. This kit is only for mechanical pulse pumps on carbureted 2-stroke engines.\u003c\/p\u003e\n\n\u003ch2\u003eRelated Blog Posts\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003ca href=\"\/blogs\/news\/marine-fuel-water-separator-guide-why-your-outboard-needs-one-and-how-to-choose\"\u003eMarine Fuel Water Separator Guide: Why Your Outboard Needs One\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/blogs\/news\/cummins-onan-rv-generator-fuel-pump-filter-149-2341-01-replacement-guide\"\u003eCummins Onan RV Generator Fuel Pump \u0026amp; Filter Replacement Guide\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/ifjf.net\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Repair Kits\",\"item\":\"https:\/\/ifjf.net\/collections\/repair-kits\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"18-7817 Fuel Pump Kit for Mercury Mariner Outboard\"}]}\n\u003c\/script\u003e","brand":"iFJF","offers":[{"title":"Default Title","offer_id":45935193129206,"sku":"FJ-CRRK54","price":35.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0606\/3836\/3894\/files\/image_1_1_1_818abec2-5568-48ad-bb5b-c13583a69015.jpg?v=1706495948","url":"https:\/\/ifjf.net\/products\/ifjf-18-7817-fuel-pump-kit-diaphragm-washer-kit-for-mercury-mariner-outboard-21-857005a1-1","provider":"iFJF Direct","version":"1.0","type":"link"}