{"product_id":"water-pump-repair-kit-fits-mercury-mariner-25-50hp-replaces-821354a2-821354a1","title":"Water Pump Repair Kit – Fits Mercury\/Mariner 25–50HP (Replaces 821354A2, 821354A1)","description":"\u003csection\u003e\n\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\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis \u003cstrong\u003eWater Pump Repair Kit for Mercury\/Mariner 25–50HP (Replaces 821354A2)\u003c\/strong\u003e is designed for a wide range of 2-stroke and 4-stroke outboard engines. It provides the essential components needed to restore the engine's cooling system to optimal performance, preventing overheating and ensuring reliability on the water.\u003c\/p\u003e\n\u003cp\u003eIt serves as a direct replacement for Mercury\/Mariner part numbers 821354A2 and 821354A1, and interchanges with Sierra 18-4531, GLM 12045, and SEI 3219.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eEngineered for direct OEM replacement installation.\u003c\/li\u003e\n  \u003cli\u003eIncludes all essential gaskets, seals, and a new impeller.\u003c\/li\u003e\n  \u003cli\u003eBuilt with OEM-quality components for durability.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eUse this matrix to confirm equivalent references across OEM and aftermarket.\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\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e821354A1\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-4531\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eGLM\u003c\/td\u003e\n        \u003ctd\u003e12045\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSEI\u003c\/td\u003e\n        \u003ctd\u003e3219\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eEngine \u0026amp; Model Compatibility\u003c\/h2\u003e\n\u003cp\u003eConfirm your engine model\/year in the table below.\u003c\/p\u003e\n\u003cp\u003eThis kit fits a variety of Mercury and Mariner outboards. Please verify your engine's serial number against the notes provided, as fitment can be specific.\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\u003eRated HP\u003c\/th\u003e\n        \u003cth\u003eStroke\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\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e25HP\u003c\/td\u003e\n        \u003ctd\u003e25\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e25HP\u003c\/td\u003e\n        \u003ctd\u003e25\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003eSerial numbers: 0G531301 and up\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e30HP\u003c\/td\u003e\n        \u003ctd\u003e30\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e30HP\u003c\/td\u003e\n        \u003ctd\u003e30\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003eSerial numbers: 0G053314 and up\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e30HP Jet\u003c\/td\u003e\n        \u003ctd\u003e30\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003eSerial numbers: 0G590000 to 0T408999, 9973100 to 0P153499\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e40HP\u003c\/td\u003e\n        \u003ctd\u003e40\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e40HP\u003c\/td\u003e\n        \u003ctd\u003e40\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003eSerial numbers: 0G531301 and up (2 cyl), 0G590000 and up (3 cyl)\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e45HP\u003c\/td\u003e\n        \u003ctd\u003e45\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e50HP\u003c\/td\u003e\n        \u003ctd\u003e50\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\/Mariner\u003c\/td\u003e\n        \u003ctd\u003e50HP\u003c\/td\u003e\n        \u003ctd\u003e50\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e821354A2\u003c\/td\u003e\n        \u003ctd\u003eSerial numbers: 0G590000 and up (3 cyl)\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specs\u003c\/h2\u003e\n\u003cdl\u003e\n  \u003cdt\u003eProduct Type\u003c\/dt\u003e\n\u003cdd\u003eWater Pump Repair Kit\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n\u003cdd\u003eDirect OEM replacement\u003c\/dd\u003e\n  \u003cdt\u003eOther Technical Attributes\u003c\/dt\u003e\n\u003cdd\u003eOEM-quality replacement parts\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e1 x Water Pump Impeller\u003c\/li\u003e\n  \u003cli\u003e1 x Drive Key\u003c\/li\u003e\n  \u003cli\u003e1 x Face Plate\u003c\/li\u003e\n  \u003cli\u003e1 x Upper Gasket (27-822189)\u003c\/li\u003e\n  \u003cli\u003e1 x Lower Gasket (27-822217)\u003c\/li\u003e\n  \u003cli\u003e2 x Washer (12-866451)\u003c\/li\u003e\n  \u003cli\u003e1 x Water Tube Seal\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eDisconnect the negative battery cable before beginning work.\u003c\/li\u003e\n  \u003cli\u003ePlace a drain pan under the lower unit and remove the gear lube drain\/fill screws to empty the oil.\u003c\/li\u003e\n  \u003cli\u003eRemove the bolts securing the lower unit (gearcase) to the engine's midsection and carefully lower it.\u003c\/li\u003e\n  \u003cli\u003eUnscrew the water pump housing bolts and lift the housing off the driveshaft.\u003c\/li\u003e\n  \u003cli\u003eNote the rotational direction of the old impeller vanes before removing the impeller, gaskets, and face plate.\u003c\/li\u003e\n  \u003cli\u003eThoroughly clean all mating surfaces, removing any old gasket material or debris.\u003c\/li\u003e\n  \u003cli\u003eInstall the new lower gasket, face plate, and drive key.\u003c\/li\u003e\n  \u003cli\u003eSlide the new impeller onto the driveshaft while turning the shaft clockwise to correctly seat the vanes inside the housing.\u003c\/li\u003e\n  \u003cli\u003eInstall the new upper gasket and reinstall the water pump housing, tightening bolts to the manufacturer's specified torque.\u003c\/li\u003e\n  \u003cli\u003eReattach the lower unit to the engine and refill the gearcase with new marine gear lube.\u003c\/li\u003e\n  \u003cli\u003eReconnect the battery and start the engine in water, ensuring a steady stream of water exits the tell-tale port.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow do I know if this kit fits my specific engine model?\u003c\/summary\u003e\n  \u003cp\u003eThis kit is designed for a range of Mercury\/Mariner 25–50HP engines. The most reliable method for confirming fitment is to check the \"Engine \u0026amp; Model Compatibility\" table and match your engine's serial number to the ranges provided. If your model is listed but serial number is not, visually compare the parts in the photos to your existing parts before ordering.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are the signs of a failing water pump?\u003c\/summary\u003e\n  \u003cp\u003eCommon signs include a weak, intermittent, or completely absent water stream from the engine's \"tell-tale\" outlet. Other indicators are engine overheating alarms, steam from the exhaust, or finding a brittle, cracked, or melted impeller during a routine inspection.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow often should the water pump impeller be replaced?\u003c\/summary\u003e\n  \u003cp\u003eFor preventative maintenance, it is highly recommended to inspect the impeller each season and replace the complete water pump repair kit every 2-3 years or 200-300 hours of operation, whichever occurs first. Service intervals should be shorter for boats operating in saltwater or sandy\/silty conditions.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eDoes this kit include the plastic water pump housing?\u003c\/summary\u003e\n  \u003cp\u003eNo, this is a repair kit containing the internal wear parts (impeller, gaskets, plate, etc.). It is designed to be installed into your existing, undamaged water pump housing.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eMy engine's serial number isn't in the compatibility list. Will this part still fit?\u003c\/summary\u003e\n  \u003cp\u003eThe serial numbers listed represent confirmed applications. If your serial number does not appear or fall within the specified ranges, this kit may not be correct for your engine. We do not recommend purchasing if your serial number does not match.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eIs any special grease needed for installation?\u003c\/summary\u003e\n  \u003cp\u003eApplying a light coat of marine grease or a soap-and-water solution to the inside of the pump housing and to the impeller vanes can ease installation and provide initial lubrication. Do not use petroleum-based grease, as it can damage the impeller rubber over time.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eOEM vs. Aftermarket?\u003c\/summary\u003e\n  \u003cp\u003eThis listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eShipping speed \u0026amp; cost\u003c\/summary\u003e\n  \u003cp\u003eWe ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWarranty \u0026amp; returns\u003c\/summary\u003e\n  \u003cp\u003eCovered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused \u0026amp; in original condition). See our policy page or reach out for instructions.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify images\/specifications vs 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, not an OEM component.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended for safety and performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\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 QC.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50723806675259,"sku":"SIE-18KM007","price":25.5,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/Water_Pump_Impeller_Kit_for_Mercury_25_-_30_-_40_-_45_-_50_HP_821354A2_-_JLM_MARINE-8290152.jpg?v=1763032271","url":"https:\/\/seasierra.com\/products\/water-pump-repair-kit-fits-mercury-mariner-25-50hp-replaces-821354a2-821354a1","provider":"SeaSierra","version":"1.0","type":"link"}