{"product_id":"water-pump-wear-plate-fits-yamaha-25hp-30hp-40hp-50hp-55hp-replaces-663-44323-00-18-3436-81420m","title":"Water Pump Wear Plate – Fits Yamaha 25HP 30HP 40HP 50HP 55HP (Replaces 663-44323-00, 18-3436, 81420M)","description":"\u003cstyle\u003e\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\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  table.ss-table th {\n    white-space:nowrap;\n    word-break:normal;\n    letter-spacing:normal;\n    font-weight:600;\n    background:#f8fafc;\n  }\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 Wear Plate\u003c\/strong\u003e is engineered as a direct replacement for Yamaha outboard lower units ranging from 25HP to 55HP, covering both 2-stroke engines manufactured between 1984 and 1996. Compatible models include Yamaha 25J, 25JEO, 25ESH, 25Q, 25QEO, 30DE, 30DEO, 30D, 30DMH, 30DEL, 30ELH, 40N, 40H, 40HE, 40QE, 40JWH, 40QM, 40QWC, 40JMH, 50HP, 50ETN, 50D, 50DEO, 50DEMTO, 50 Pro Series, P50, 55ED, 55ET, 55B, 55BM, and 55BT.\u003c\/p\u003e\n\n\u003cp\u003eThis aftermarket wear plate directly replaces OEM part number 663-44323-00 and cross-references with Sierra 18-3436 and Mercury Marine 81420M.\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003eEssential water pump component designed to protect the impeller and housing\u003c\/li\u003e\n\u003cli\u003ePrecision-engineered for proper clearance and flow in Yamaha lower units\u003c\/li\u003e\n\u003cli\u003eDrop-in installation during routine water pump service or rebuild\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\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\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e663-44323-00\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-3436\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury Marine\u003c\/td\u003e\n        \u003ctd\u003e81420M\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\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\u003eYears\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e25J \/ 25JEO \/ 25ESH\u003c\/td\u003e\n        \u003ctd\u003e25\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e25Q \/ 25QEO\u003c\/td\u003e\n        \u003ctd\u003e25\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e30DE \/ 30DEO \/ 30D\u003c\/td\u003e\n        \u003ctd\u003e30\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e30DMH \/ 30DEL \/ 30ELH\u003c\/td\u003e\n        \u003ctd\u003e30\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e40N \/ 40H \/ 40HE \/ 40QE \/ 40JWH \/ 40QM \/ 40QWC\u003c\/td\u003e\n        \u003ctd\u003e40\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1984–1994\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e40JMH\u003c\/td\u003e\n        \u003ctd\u003e40\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e50HP \/ 50ETN \/ 50D \/ 50DEO \/ 50DEMTO\u003c\/td\u003e\n        \u003ctd\u003e50\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1984–1987\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e50 (Pro Series 50)\u003c\/td\u003e\n        \u003ctd\u003e50\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1987–1990\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eP50\u003c\/td\u003e\n        \u003ctd\u003e50\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1995–1996\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e55ED\u003c\/td\u003e\n        \u003ctd\u003e55\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e55ET\u003c\/td\u003e\n        \u003ctd\u003e55\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003e55B \/ 55BM \/ 55BT\u003c\/td\u003e\n        \u003ctd\u003e55\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\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\u003eOEM Part Number\u003c\/dt\u003e\n  \u003cdd\u003e663-44323-00\u003c\/dd\u003e\n  \u003cdt\u003eReplaces\u003c\/dt\u003e\n  \u003cdd\u003eSierra 18-3436, Mercury Marine 81420M\u003c\/dd\u003e\n  \u003cdt\u003eApplication\u003c\/dt\u003e\n  \u003cdd\u003eYamaha Outboard Lower Unit Water Pump\u003c\/dd\u003e\n  \u003cdt\u003eEngine Type\u003c\/dt\u003e\n  \u003cdd\u003e2-Stroke\u003c\/dd\u003e\n  \u003cdt\u003eHorsepower Range\u003c\/dt\u003e\n  \u003cdd\u003e25HP – 55HP\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1×\u003c\/strong\u003e Impeller Wear Plate: 663-44323-00\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n\u003cli\u003eDisconnect the battery and remove the lower unit from the outboard following the manufacturer's service manual.\u003c\/li\u003e\n\u003cli\u003eRemove the existing water pump housing and carefully extract the old impeller and wear plate.\u003c\/li\u003e\n\u003cli\u003eClean all mating surfaces thoroughly, removing old gasket material and debris.\u003c\/li\u003e\n\u003cli\u003ePosition the new wear plate in the pump housing with the correct side facing the impeller.\u003c\/li\u003e\n\u003cli\u003eInstall the impeller, ensuring the vanes are oriented correctly per the rotation direction indicated in the housing.\u003c\/li\u003e\n\u003cli\u003eApply marine-grade grease to the impeller vanes to aid initial priming and prevent dry starts.\u003c\/li\u003e\n\u003cli\u003eReassemble the water pump housing with a new gasket set and torque fasteners to manufacturer specifications.\u003c\/li\u003e\n\u003cli\u003eReinstall the lower unit and reconnect all fittings and shift linkages.\u003c\/li\u003e\n\u003cli\u003eTest the cooling system by running the engine in a test tank or on-water; verify steady water discharge from the tell-tale.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\u003csummary\u003eHow do I know if my wear plate needs replacement?\u003c\/summary\u003e\u003cp\u003eInspect the wear plate during routine water pump service. Replace if you notice deep grooves, cracks, warping, or excessive wear that could allow the impeller to contact metal surfaces. Most technicians replace the wear plate whenever the impeller is changed.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eWill this fit all Yamaha 40HP–50HP engines?\u003c\/summary\u003e\u003cp\u003eThis wear plate fits specific 2-stroke Yamaha models from 1984–1996 as listed in the compatibility table. Always cross-reference your engine's serial number and original part number to confirm fitment before ordering.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eCan I reuse the old wear plate when installing a new impeller?\u003c\/summary\u003e\u003cp\u003eIt is not recommended. Worn or grooved wear plates reduce impeller efficiency, increase friction, and can cause premature impeller failure. Always replace the wear plate as part of a complete water pump rebuild.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eWhat happens if the wear plate is installed backwards?\u003c\/summary\u003e\u003cp\u003eInstalling the wear plate in reverse can disrupt water flow, cause impeller damage, and lead to overheating. Ensure the correct orientation per the pump housing markings or service manual.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eHow often should I replace the wear plate?\u003c\/summary\u003e\u003cp\u003eReplace the wear plate every time you service the water pump or impeller, typically every 2–3 years or 200–300 hours of operation, whichever comes first. Saltwater use may require more frequent intervals.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eOEM vs. Aftermarket?\u003c\/summary\u003e\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\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eDoes this come with gaskets or other pump components?\u003c\/summary\u003e\u003cp\u003eNo. This listing includes only the wear plate. Gaskets, impeller, housing, and other water pump components are sold separately. We recommend purchasing a complete water pump rebuild kit for comprehensive service.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eShipping speed \u0026amp; cost\u003c\/summary\u003e\u003cp\u003eWe ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdetails\u003e\u003csummary\u003eWarranty \u0026amp; returns\u003c\/summary\u003e\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\u003c\/details\u003e\n\n\u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eVerify images\/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, 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\u003ePro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.\u003c\/li\u003e\n\u003cli\u003eFast Global Fulfillment — Free standard delivery to most regions in 5–15 days.\u003c\/li\u003e\n\u003cli\u003eManufacturer-Direct Value — Fair pricing without compromising on materials or QC.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":51025605099835,"sku":"2332","price":13.98,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/A199dd27c494946a8b1e56e0cf6583672e.webp?v=1772931813","url":"https:\/\/seasierra.com\/products\/water-pump-wear-plate-fits-yamaha-25hp-30hp-40hp-50hp-55hp-replaces-663-44323-00-18-3436-81420m","provider":"SeaSierra","version":"1.0","type":"link"}