{"product_id":"water-pump-impeller-kit-fits-yamaha-40-50hp-2-stroke-outboards-replaces-6h4-w0078-00-00-18-3429","title":"Water Pump Impeller Kit – Fits Yamaha 40–50HP 2-Stroke Outboards (Replaces 6H4-W0078-00-00, 18-3429)","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 complete \u003cstrong\u003eWater Pump Impeller Kit – Fits Yamaha 40–50HP 2-Stroke Outboards (Replaces 6H4-W0078-00-00)\u003c\/strong\u003e provides all necessary components for a full water pump service. It is specifically designed for Yamaha 40HP (1984–1994), 50HP standard models (1984–1987), Pro Series 50 (1987–1990), and P50 Series (1995–1996) outboards.\u003c\/p\u003e\n    \u003cp\u003eIt serves as a direct interchange for Yamaha part numbers 6H4-W0078-00-00, 6H4-W0078-01-00, and 6H4-W0078-A0-00, as well as aftermarket equivalents like Sierra 18-3429 and SouthMarine 6H4-W0078-A0\/6H4-W0078-00.\u003c\/p\u003e\n    \u003cul\u003e\n        \u003cli\u003eEngineered for a direct OEM-replacement installation process.\u003c\/li\u003e\n        \u003cli\u003eFeatures a durable, heat-resistant neoprene impeller for reliable cooling performance.\u003c\/li\u003e\n        \u003cli\u003eIncludes all required gaskets, stainless steel hardware, and a Woodruff key for a comprehensive overhaul.\u003c\/li\u003e\n    \u003c\/ul\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n    \u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n    \u003cp\u003eUse this matrix to confirm equivalent references across OEM and aftermarket suppliers.\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\u003eYamaha\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-00-00\u003c\/td\u003e\n                \u003c\/tr\u003e\n                \u003ctr\u003e\n                    \u003ctd\u003eYamaha\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-01-00\u003c\/td\u003e\n                \u003c\/tr\u003e\n                \u003ctr\u003e\n                    \u003ctd\u003eYamaha\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-A0-00\u003c\/td\u003e\n                \u003c\/tr\u003e\n                \u003ctr\u003e\n                    \u003ctd\u003eSierra\u003c\/td\u003e\n                    \u003ctd\u003e18-3429\u003c\/td\u003e\n                \u003c\/tr\u003e\n                \u003ctr\u003e\n                    \u003ctd\u003eSouthMarine\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-A0\u003c\/td\u003e\n                \u003c\/tr\u003e\n                 \u003ctr\u003e\n                    \u003ctd\u003eSouthMarine\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-00\u003c\/td\u003e\n                \u003c\/tr\u003e\n            \u003c\/tbody\u003e\n        \u003c\/table\u003e\n    \u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n    \u003ch2\u003eEngine \u0026amp; Model Compatibility\u003c\/h2\u003e\n    \u003cp\u003eConfirm your engine model and year in the table below.\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\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\u003eYamaha\u003c\/td\u003e\n                    \u003ctd\u003eAll models\u003c\/td\u003e\n                    \u003ctd\u003e40\u003c\/td\u003e\n                    \u003ctd\u003e2-Stroke\u003c\/td\u003e\n                    \u003ctd\u003e1984–1994\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-00-00\u003c\/td\u003e\n                    \u003ctd\u003e\u003c\/td\u003e\n                \u003c\/tr\u003e\n                \u003ctr\u003e\n                    \u003ctd\u003eYamaha\u003c\/td\u003e\n                    \u003ctd\u003eStandard models\u003c\/td\u003e\n                    \u003ctd\u003e50\u003c\/td\u003e\n                    \u003ctd\u003e2-Stroke\u003c\/td\u003e\n                    \u003ctd\u003e1984–1987\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-00-00\u003c\/td\u003e\n                    \u003ctd\u003e\u003c\/td\u003e\n                \u003c\/tr\u003e\n                \u003ctr\u003e\n                    \u003ctd\u003eYamaha\u003c\/td\u003e\n                    \u003ctd\u003ePro 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                    \u003ctd\u003e6H4-W0078-00-00\u003c\/td\u003e\n                    \u003ctd\u003e\u003c\/td\u003e\n                \u003c\/tr\u003e\n                \u003ctr\u003e\n                    \u003ctd\u003eYamaha\u003c\/td\u003e\n                    \u003ctd\u003eP50 Series\u003c\/td\u003e\n                    \u003ctd\u003e50\u003c\/td\u003e\n                    \u003ctd\u003e2-Stroke\u003c\/td\u003e\n                    \u003ctd\u003e1995–1996\u003c\/td\u003e\n                    \u003ctd\u003e6H4-W0078-00-00\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\u003c\/section\u003e\n\u003csection\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 OEM replacement\u003c\/dd\u003e\n        \u003cdt\u003eHousing Material\u003c\/dt\u003e\n\u003cdd\u003eMetal\/Plastic composite\u003c\/dd\u003e\n        \u003cdt\u003eImpeller Material\u003c\/dt\u003e\n\u003cdd\u003eNeoprene (heat-resistant, flexible)\u003c\/dd\u003e\n        \u003cdt\u003eHardware Material\u003c\/dt\u003e\n\u003cdd\u003eStainless steel\u003c\/dd\u003e\n        \u003cdt\u003eGaskets\u003c\/dt\u003e\n\u003cdd\u003eNon-asbestos fiber (OEM-compliant)\u003c\/dd\u003e\n        \u003cdt\u003eBlade Count\u003c\/dt\u003e\n\u003cdd\u003e6\u003c\/dd\u003e\n        \u003cdt\u003eWarranty\u003c\/dt\u003e\n\u003cdd\u003e30 days (retailer dependent)\u003c\/dd\u003e\n    \u003c\/dl\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n    \u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n    \u003cul\u003e\n        \u003cli\u003e1 × Water Pump Impeller (6H4-44352-00)\u003c\/li\u003e\n        \u003cli\u003e1 × Insert Cup (663-44322-00)\u003c\/li\u003e\n        \u003cli\u003e1 × Wear Plate (663-44323-00)\u003c\/li\u003e\n        \u003cli\u003e1 × Gasket (663-44315-A0)\u003c\/li\u003e\n        \u003cli\u003e1 × Gasket (663-44316-A0)\u003c\/li\u003e\n        \u003cli\u003e1 × Gasket (663-44324-A0)\u003c\/li\u003e\n        \u003cli\u003e1 × Grommet (663-44366-00)\u003c\/li\u003e\n        \u003cli\u003e2 × Bolts (97080-08045)\u003c\/li\u003e\n        \u003cli\u003e2 × Bolts (97080-08055)\u003c\/li\u003e\n        \u003cli\u003e1 × Woodruff Key (90280-03024)\u003c\/li\u003e\n    \u003c\/ul\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n    \u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n    \u003col\u003e\n        \u003cli\u003eDisconnect the battery and shift the outboard into neutral.\u003c\/li\u003e\n        \u003cli\u003eDrain the lower unit gear oil completely to prevent spills.\u003c\/li\u003e\n        \u003cli\u003eRemove the lower unit mounting bolts and carefully detach the lower unit from the engine.\u003c\/li\u003e\n        \u003cli\u003eLocate and unbolt the water pump housing to access the impeller.\u003c\/li\u003e\n        \u003cli\u003eRemove the old impeller, wear plate, insert cup, and gaskets. Note the rotational direction of the old impeller vanes for correct installation of the new one.\u003c\/li\u003e\n        \u003cli\u003eThoroughly clean all mating surfaces, removing any old gasket material or sealant.\u003c\/li\u003e\n        \u003cli\u003eInstall the new gaskets, wear plate, and cup. Apply a light coat of marine grease to the inside of the housing.\u003c\/li\u003e\n        \u003cli\u003eSlide the new Woodruff key onto the driveshaft and then slide the new impeller on, turning the shaft clockwise to bend the vanes into position.\u003c\/li\u003e\n        \u003cli\u003eReinstall the pump housing, ensuring a proper seal. Tighten bolts to the manufacturer's specified torque.\u003c\/li\u003e\n        \u003cli\u003eRe-attach the lower unit, reconnecting the shift shaft and water tube. Refill the lower unit with fresh gear oil before operation.\u003c\/li\u003e\n    \u003c\/ol\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n    \u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n    \u003cdetails\u003e\n        \u003csummary\u003eHow can I confirm this kit fits my specific engine?\u003c\/summary\u003e\n        \u003cp\u003eYour model must be listed in the Engine \u0026amp; Model Compatibility table. Please check your engine's model, horsepower, and year range against the table. If your model is not listed, this kit may not fit.\u003c\/p\u003e\n    \u003c\/details\u003e\n    \u003cdetails\u003e\n        \u003csummary\u003eWhat are the signs of a failing water pump impeller?\u003c\/summary\u003e\n        \u003cp\u003eCommon symptoms include the engine overheating at idle or low speeds, a weak or non-existent stream of water from the \"tell-tale\" outlet, and in severe cases, an engine alarm. A brittle or cracked impeller upon inspection also indicates it's time for replacement.\u003c\/p\u003e\n    \u003c\/details\u003e\n    \u003cdetails\u003e\n        \u003csummary\u003eHow often should I replace my outboard's impeller?\u003c\/summary\u003e\n        \u003cp\u003eAs a general maintenance rule, it is recommended to replace the impeller every 1-2 years or every 100-200 hours of use, whichever comes first. For boats operated in saltwater or sandy\/silty conditions, annual replacement is strongly advised.\u003c\/p\u003e\n    \u003c\/details\u003e\n    \u003cdetails\u003e\n        \u003csummary\u003eWhy is my engine still overheating after installing the new kit?\u003c\/summary\u003e\n        \u003cp\u003eIf overheating persists, verify the impeller was installed with the vanes rotating in the correct direction (typically clockwise). Check for blockages in the cooling water passages, intake screens, or the tell-tale outlet. Ensure the thermostat is functioning correctly, as it could be stuck closed.\u003c\/p\u003e\n    \u003c\/details\u003e\n    \u003cdetails\u003e\n        \u003csummary\u003eIs there a difference between OEM and this aftermarket kit?\u003c\/summary\u003e\n        \u003cp\u003eThis listing is an aftermarket replacement, not an original equipment manufacturer (OEM) part. It has été built to meet or exceed OEM-level specifications using comparable high-quality materials. Our parts are manufactured in an ISO 9002 certified facility and are batch-inspected to ensure consistent quality and performance.\u003c\/p\u003e\n    \u003c\/details\u003e\n    \u003cdetails\u003e\n        \u003csummary\u003eWhat are the shipping speed and cost?\u003c\/summary\u003e\n        \u003cp\u003eWe ship worldwide quickly, with typical transit times of 5–15 days for most regions. Standard shipping is free for all orders. Expedited shipping options and their costs will be displayed at checkout if available for your location.\u003c\/p\u003e\n    \u003c\/details\u003e\n    \u003cdetails\u003e\n        \u003csummary\u003eWhat is the warranty and return policy?\u003c\/summary\u003e\n        \u003cp\u003eThis kit is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard window, provided the item is unused and in its original packaging. Please see our full policy page or reach out for detailed instructions.\u003c\/p\u003e\n    \u003c\/details\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n    \u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n    \u003cul\u003e\n        \u003cli\u003eVerify all images and specifications against your original part before ordering. If anything differs—even if your model appears on the compatibility list—do not purchase.\u003c\/li\u003e\n        \u003cli\u003eThis is an aftermarket replacement component, not an OEM part. Reference numbers are provided for interchange purposes only.\u003c\/li\u003e\n        \u003cli\u003eProfessional installation by a qualified marine mechanic is highly recommended for safety, performance, and to prevent damage to your engine.\u003c\/li\u003e\n    \u003c\/ul\u003e\n\u003c\/section\u003e\n\u003csection\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 rigorously tested for demanding real-world conditions.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003eFast Global Fulfillment\u003c\/strong\u003e — We offer free standard delivery to most regions, with parts typically arriving in 5–15 days from our integrated logistics network.\u003c\/li\u003e\n        \u003cli\u003e\n\u003cstrong\u003eManufacturer-Direct Value\u003c\/strong\u003e — By working directly with our manufacturing partners, we provide 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":50723973955899,"sku":"22KY026","price":36.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/22KY026_1_3d96c961-5dea-42e1-9da4-4db24678e1fe.jpg?v=1763038932","url":"https:\/\/seasierra.com\/products\/water-pump-impeller-kit-fits-yamaha-40-50hp-2-stroke-outboards-replaces-6h4-w0078-00-00-18-3429","provider":"SeaSierra","version":"1.0","type":"link"}