{"product_id":"water-pump-impeller-kit-fits-mercury-r-mr-alpha-one-replaces-42724a3","title":"Water Pump Impeller Kit – Fits Mercury R\/MR\/Alpha One (Replaces 42724A3)","description":"\u003c!-- 🔧 Table Styles (include only once per page) --\u003e\n\u003cstyle\u003e\n  \/* Outer container allows horizontal scrolling (with iOS momentum) *\/\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\n\n  \/* Base table styles *\/\n  table.ss-table { width:100%; border-collapse:collapse; min-width:640px; }\n  table.ss-table th, table.ss-table td {\n    padding:10px 12px; border:1px solid #e5e7eb; text-align:left; vertical-align:top;\n  }\n\n  \/* Key: prevent wrapping, word breaks, and vertical text in headers *\/\n  table.ss-table th {\n    white-space:nowrap;       \/* Do not wrap *\/\n    word-break:normal;        \/* Don’t break words *\/\n    letter-spacing:normal;    \/* Prevent theme styles from stretching letters *\/\n    font-weight:600;\n    background:#f8fafc;\n  }\n\n  \/* Small screen optimization *\/\n  @media (max-width:480px){\n    table.ss-table th, table.ss-table td { padding:8px 10px; font-size:14px; }\n  }\n\u003c\/style\u003e\n\u003csection\u003e\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis \u003cstrong\u003eWater Pump Impeller Kit\u003c\/strong\u003e is designed for Mercury Marine R, MR, and Alpha One Generation I sterndrives manufactured between 1984 and 1990 (serial numbers 6854393 to OD469858). It provides the essential components for servicing the lower unit's water pump.\u003c\/p\u003e\n\u003cp\u003eIt serves as a direct interchange for several original and aftermarket part numbers, including Mercury 42724A3, Mercury 46-37433A1, Sierra 18-3219, and GLM 12200.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eEngineered as a direct replacement for a straightforward installation.\u003c\/li\u003e\n\u003cli\u003eCompatible with Generation 1 (Alpha I) and MR model Mercruiser lower unit outdrives.\u003c\/li\u003e\n\u003cli\u003eIncludes the impeller, pocket cover, and guide tube for a complete service.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eUse this matrix to confirm equivalent references across OEM and aftermarket brands.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Part Number Matrix\"\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\u003e42724A3\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e46-37433A1\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-3219\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eGLM\u003c\/td\u003e\n        \u003ctd\u003e12200\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\u003ch2\u003eEngine \u0026amp; Model Compatibility\u003c\/h2\u003e\n\u003cp\u003eConfirm your engine model and year in the table below to ensure accurate fitment.\u003c\/p\u003e\n\u003cp\u003eFor Mercury Marine engines, this kit is specifically designed for the R, MR, and Alpha One (Gen I) sterndrive models within the specified serial number ranges.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Engine \u0026amp; Model Compatibility\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eBrand\u003c\/th\u003e\n        \u003cth\u003eModel\u003c\/th\u003e\n        \u003cth\u003eYears\u003c\/th\u003e\n        \u003cth\u003eOEM Part No.\u003c\/th\u003e\n        \u003cth\u003eNotes\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\u003eR\u003c\/td\u003e\n        \u003ctd\u003e1967–1990\u003c\/td\u003e\n        \u003ctd\u003e42724A3\u003c\/td\u003e\n        \u003ctd\u003eFor serial numbers 2495186–OD469858\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003eMR\u003c\/td\u003e\n        \u003ctd\u003e1967–1990\u003c\/td\u003e\n        \u003ctd\u003e42724A3\u003c\/td\u003e\n        \u003ctd\u003eFor serial numbers 2495186–OD469858\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003eAlpha One Gen I\u003c\/td\u003e\n        \u003ctd\u003e1984–1990\u003c\/td\u003e\n        \u003ctd\u003e42724A3\u003c\/td\u003e\n        \u003ctd\u003eFor serial numbers 6854393–OD469858\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\u003ch2\u003eTechnical Specs\u003c\/h2\u003e\n\u003cdl\u003e\n  \u003cdt\u003eProduct Type\u003c\/dt\u003e\n\u003cdd\u003eWater Pump Impeller Kit\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n\u003cdd\u003eDirect replacement\u003c\/dd\u003e\n  \u003cdt\u003eCompatibility\u003c\/dt\u003e\n\u003cdd\u003eCompatible with Generation 1 (Alpha I) and MR model Mercruiser lower unit outdrives\u003c\/dd\u003e\n\u003c\/dl\u003e\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e1 x Water Pump Impeller Kit (Replaces 42724A3) including:\u003c\/li\u003e\n  \u003cli\u003e1 x Pocket Cover (42724A3)\u003c\/li\u003e\n  \u003cli\u003e1 x Guide Tube (23-29804T)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n\u003cli\u003eDisconnect the negative battery cable for safety.\u003c\/li\u003e\n\u003cli\u003eShift the sterndrive into the forward gear position.\u003c\/li\u003e\n\u003cli\u003eRemove the lower unit (gearcase) from the upper housing by undoing the main bolts.\u003c\/li\u003e\n\u003cli\u003eUnbolt and carefully remove the old water pump housing assembly from the lower unit.\u003c\/li\u003e\n\u003cli\u003eThoroughly clean the mating surfaces of any old gasket material or debris.\u003c\/li\u003e\n\u003cli\u003eAssemble the new impeller, key, and plate from the kit into the new housing.\u003c\/li\u003e\n\u003cli\u003eApply a light coat of marine grease to the inside of the pump housing and the impeller vanes.\u003c\/li\u003e\n\u003cli\u003eInstall the new pump assembly onto the driveshaft. Gently turn the shaft clockwise to help seat the impeller vanes in the correct direction.\u003c\/li\u003e\n\u003cli\u003eSecurely bolt the new pump assembly in place, tightening to the manufacturer's torque specifications.\u003c\/li\u003e\n\u003cli\u003eReinstall the lower unit, ensuring the water tube and shift shaft are properly aligned.\u003c\/li\u003e\n\u003cli\u003eReconnect the battery, supply cooling water to the drive, and briefly run the engine to check for proper water flow.\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\u003csummary\u003eHow do I confirm if this kit fits my sterndrive?\u003c\/summary\u003e\u003cp\u003eThis kit is specifically for Mercury R, MR, and Alpha One Generation I drives from 1984–1990, within serial numbers 6854393 to OD469858. Always verify your sterndrive model and serial number range against the compatibility table before ordering.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWhat are the signs of a bad water pump impeller?\u003c\/summary\u003e\u003cp\u003eThe most common symptoms are engine overheating, especially at idle, a weak or non-existent water stream from the tell-tale outlet, and a dry, cracked, or brittle appearance of the old impeller upon inspection.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eHow often should I replace my sterndrive's impeller?\u003c\/summary\u003e\u003cp\u003eFor preventative maintenance, it is recommended to replace the impeller every 1 to 2 years or every 100-200 hours of operation. Frequency should be increased if you operate in saltwater or water with high levels of sand or silt.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eDoes this kit include the full pump housing?\u003c\/summary\u003e\u003cp\u003eThis kit includes the key service components: the impeller, a pocket cover, and a guide tube. Please refer to the \"What’s in the Box\" section and product images to ensure it matches your specific repair needs.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eOEM vs. Aftermarket?\u003c\/summary\u003e\u003cp\u003eThis listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility, where it is batch-inspected for consistency.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eShipping speed \u0026amp; cost?\u003c\/summary\u003e\u003cp\u003eWe ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free, and expedited options may appear at checkout where available.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWarranty \u0026amp; returns?\u003c\/summary\u003e\u003cp\u003eOur parts are covered by a 1-year warranty against manufacturing defects under normal use. If an issue arises, contact our support team with your order details. Returns are accepted within our standard window for unused items in original condition. See our policy page or reach out for instructions.\u003c\/p\u003e\u003c\/details\u003e\n\u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eVerify images and specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.\u003c\/li\u003e\n\u003cli\u003eThis is an aftermarket replacement part, not an OEM component.\u003c\/li\u003e\n\u003cli\u003eProfessional installation is recommended for safety and optimal performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eAbout Sea Sierra\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePro-Grade Standards\u003c\/strong\u003e — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast Global Fulfillment\u003c\/strong\u003e — Free standard delivery to most regions in 5–15 days.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer-Direct Value\u003c\/strong\u003e — Fair pricing without compromising on materials or quality control.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50717885759803,"sku":"22KM017","price":32.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/Water_Pump_Impeller_Kit_for_Mercury_R-MR-Alpha_One_42724A3_-_JLM_MARINE-8290012.jpg?v=1762937340","url":"https:\/\/seasierra.com\/products\/water-pump-impeller-kit-fits-mercury-r-mr-alpha-one-replaces-42724a3","provider":"SeaSierra","version":"1.0","type":"link"}