{"product_id":"sierra-18-3012-impeller-for-mercury-outboards","title":"Sierra 18-3012 Impeller for Mercury Outboards","description":"\u003cp class=\"nvn-hero\"\u003eThe Sierra 18-3012 is the water pump impeller that keeps your Mercury outboard cool. Its flexible vanes push raw water up through the powerhead every time the engine runs, so a worn one means overheating. This is a single OEM-quality replacement that cross-references Mercury part 47-22748. Match your part number, swap it during your next water pump service, and stay ahead of an expensive problem.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eThe Sierra 18-3012 is the water pump impeller that keeps a Mercury outboard from cooking itself. It's a small rubber part, but it does one of the most important jobs on the whole engine. Every time you turn the key, this impeller starts spinning inside the water pump housing and pushes raw water up through the powerhead to carry heat away. No impeller, no cooling. It's that simple.\u003c\/p\u003e\n\u003cp\u003eSierra builds this one to meet or exceed the original-equipment impeller it replaces. That's the whole idea behind the Sierra line. They supply parts to plenty of engine builders and boat makers, so the fit and the material hold up to the same demands as the factory piece. For the boater doing an annual water pump service on the trailer, that means you get OEM-level performance without hunting down a dealer part.\u003c\/p\u003e\n\u003cp\u003eThis listing is a single impeller. Not a full water pump kit. We call that out up front because it matters. A complete pump rebuild usually wants gaskets, a wear plate, and sometimes the housing too, and those are separate items. If your old impeller is the only thing that's worn and the rest of your pump checks out, the 18-3012 is exactly the part you need and nothing you don't. If you're doing a full teardown, grab the supporting gaskets and hardware to go with it.\u003c\/p\u003e\n\u003cp\u003eHow do you know it's time? A weak or sputtering telltale stream, the little pee stream out the back, is the classic early warning. So is a temperature alarm or an engine that runs hotter than it should at cruise. Impeller vanes take a set over time, crack, and lose their spring, and once they can't seal against the housing the water volume drops off. Most techs recommend replacing the impeller every two to three seasons, or every couple hundred hours, whichever comes first. If you ever ran the motor dry, even for a few seconds on the hose or off the water, replace it right away. Rubber vanes shred fast without water to lubricate and cool them.\u003c\/p\u003e\n\u003cp\u003eThe vanes themselves are flexible rubber, designed to flex against the pump housing and create the pumping action as they spin. That flexibility is also why they wear. Every start-up, every hour of run time, and especially any dry run works the rubber. A fresh impeller restores the tight seal and full water volume your engine was designed around, which keeps operating temperatures where they belong and helps everything downstream, the thermostat, the poppet valve, and the cooling passages, do its job.\u003c\/p\u003e\n\u003cp\u003eInstallation is a standard water pump job. You'll drop the lower unit, pull the pump housing, slide the old impeller off the shaft, and set the new 18-3012 in place with the vanes bent the correct direction of rotation. Take your time lining up the key and the housing. It's the kind of job a lot of owners do themselves in an afternoon with basic hand tools and a service manual for the torque specs and the exact steps for your model.\u003c\/p\u003e\n\u003cp\u003eFitment is the one thing to nail down before you order. This impeller fits a range of Mercury outboard engines, and it cross-references the Mercury OEM part 47-22748. Match your part number, or check your engine's model and serial range against the application data, before you buy. Outboard water pumps changed over the years and across horsepower ranges, so confirming the number is the fastest way to be sure you're holding the right part.\u003c\/p\u003e\n\u003cp\u003eWho's this for? Anyone keeping up with regular maintenance on their Mercury outboard, from the first-time owner tackling their first pump service to the seasoned mechanic who buys these by the handful. It's an inexpensive part that prevents an expensive problem. An overheated powerhead costs a whole lot more than an impeller, so staying ahead of this one is just smart boat ownership.\u003c\/p\u003e\n\u003cp\u003eKeep a spare on the boat if you cruise far from the ramp. An impeller is cheap insurance, and swapping one at the dock beats a tow home. Order the 18-3012, confirm the fit against your engine, and you're set for another season of worry-free cooling.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003eSierra part number 18-3012, built to meet or exceed the original-equipment impeller it replaces\u003c\/li\u003e\n  \u003cli\u003eFits Mercury Marine outboard engines, restoring full raw-water cooling flow\u003c\/li\u003e\n  \u003cli\u003eFlexible rubber vanes prime the moment the engine cranks and push cooling water up to the powerhead\u003c\/li\u003e\n  \u003cli\u003eCross-references the Mercury OEM impeller 47-22748 for quick part confirmation\u003c\/li\u003e\n  \u003cli\u003eSold as a single impeller, the primary wear item in a water pump service\u003c\/li\u003e\n  \u003cli\u003eDirect-fit replacement with no trimming or modification for the engines it covers\u003c\/li\u003e\n  \u003cli\u003eBacked by Sierra's OEM-replacement engineering trusted by engine builders and boat makers\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cdiv class=\"nvn-trust\"\u003e\n  \u003ch2\u003eWhy Buy from NVN Marine\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eAuthorized Sierra Marine reseller, full manufacturer warranty\u003c\/li\u003e\n    \u003cli\u003eNMEA member and ABYC certified, advice from real boat techs\u003c\/li\u003e\n    \u003cli\u003eSame-day shipping before 3 PM ET on in-stock items\u003c\/li\u003e\n    \u003cli\u003eNY headquarters and Fort Lauderdale flagship retail store\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"nvn-faq\"\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat does the Sierra 18-3012 impeller actually do?\u003c\/summary\u003e\n    \u003cp\u003eIt's the pump that moves raw water through your outboard's cooling system. As the impeller spins inside the water pump housing, its flexible vanes push water up to the powerhead to carry heat away. If it fails, the engine loses cooling flow and can overheat fast.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhich engines does the 18-3012 fit?\u003c\/summary\u003e\n    \u003cp\u003eIt fits a range of Mercury Marine outboard engines. Water pumps changed across model years and horsepower ranges, so match your part number or check your engine's model and serial against the application data before ordering.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDoes this replace a factory Mercury impeller?\u003c\/summary\u003e\n    \u003cp\u003eYes. It cross-references the Mercury OEM part 47-22748 and is engineered to meet or exceed the original impeller it replaces.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDo I get a full water pump kit or just the impeller?\u003c\/summary\u003e\n    \u003cp\u003eJust the impeller. This is a single impeller, not a complete pump rebuild kit. If you're doing a full service you'll usually want gaskets and a wear plate too, and those are separate items.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should I replace my water pump impeller?\u003c\/summary\u003e\n    \u003cp\u003eA common guideline is every two to three seasons or every couple hundred hours, whichever comes first. If you've ever run the motor dry, even briefly, replace it right away.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat are the warning signs of a worn impeller?\u003c\/summary\u003e\n    \u003cp\u003eA weak or sputtering telltale stream out the back, higher running temperatures, or an overheat alarm. Once the vanes lose their spring they can't seal against the housing and water volume drops.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat happens if I run the engine without water?\u003c\/summary\u003e\n    \u003cp\u003eThe rubber vanes rely on water to cool and lubricate them. Run dry, even for a few seconds on the hose, and they can tear or burn quickly. If that happens, replace the impeller before your next trip.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs installation something I can do myself?\u003c\/summary\u003e\n    \u003cp\u003eFor a lot of owners, yes. It's a standard water pump job: drop the lower unit, open the pump housing, swap the impeller, and reassemble. Use your engine's service manual for the exact steps and torque values.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow do I make sure I'm ordering the right part?\u003c\/summary\u003e\n    \u003cp\u003eMatch the Sierra number 18-3012, cross-reference the Mercury OEM 47-22748, or confirm your engine's model and serial range against the application data in the specs. Confirming the number is the surest way to get the correct impeller.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eShould I keep a spare on board?\u003c\/summary\u003e\n    \u003cp\u003eIf you cruise away from the ramp, it's smart. An impeller is inexpensive and compact, and swapping one at the dock is far easier than dealing with an overheated engine on the water.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable class=\"nvn-specs\"\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003eTitle\u003c\/th\u003e\n\u003ctd\u003eSierra 18-3012 Water Pump Impeller\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003ctd\u003eSierra\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eManufacturer\u003c\/th\u003e\n\u003ctd\u003eSierra Marine\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eManufacturer Part Number\u003c\/th\u003e\n\u003ctd\u003e18-3012\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e030999237132\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePart Type\u003c\/th\u003e\n\u003ctd\u003eWater Pump Impeller\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eApplication\u003c\/th\u003e\n\u003ctd\u003eMercury Marine Outboard Engines\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eSold As\u003c\/th\u003e\n\u003ctd\u003eSingle\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePackage Contents\u003c\/th\u003e\n\u003ctd\u003eOne water pump impeller\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eReplaces Mercury OEM Part Number\u003c\/th\u003e\n\u003ctd\u003e47-22748\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMallory Cross-Reference\u003c\/th\u003e\n\u003ctd\u003e9-45308\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eGLM Cross-Reference\u003c\/th\u003e\n\u003ctd\u003e89600\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@type\": \"FAQPage\",\n    \"mainEntity\": [\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What does the Sierra 18-3012 impeller actually do?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's the pump that moves raw water through your outboard's cooling system. As the impeller spins inside the water pump housing, its flexible vanes push water up to the powerhead to carry heat away. If it fails, the engine loses cooling flow and can overheat fast.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Which engines does the 18-3012 fit?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It fits a range of Mercury Marine outboard engines. Water pumps changed across model years and horsepower ranges, so match your part number or check your engine's model and serial against the application data before ordering.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Does this replace a factory Mercury impeller?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Yes. It cross-references the Mercury OEM part 47-22748 and is engineered to meet or exceed the original impeller it replaces.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Do I get a full water pump kit or just the impeller?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Just the impeller. This is a single impeller, not a complete pump rebuild kit. If you're doing a full service you'll usually want gaskets and a wear plate too, and those are separate items.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How often should I replace my water pump impeller?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"A common guideline is every two to three seasons or every couple hundred hours, whichever comes first. If you've ever run the motor dry, even briefly, replace it right away.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What are the warning signs of a worn impeller?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"A weak or sputtering telltale stream out the back, higher running temperatures, or an overheat alarm. Once the vanes lose their spring they can't seal against the housing and water volume drops.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What happens if I run the engine without water?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"The rubber vanes rely on water to cool and lubricate them. Run dry, even for a few seconds on the hose, and they can tear or burn quickly. If that happens, replace the impeller before your next trip.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is installation something I can do myself?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"For a lot of owners, yes. It's a standard water pump job: drop the lower unit, open the pump housing, swap the impeller, and reassemble. Use your engine's service manual for the exact steps and torque values.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How do I make sure I'm ordering the right part?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Match the Sierra number 18-3012, cross-reference the Mercury OEM 47-22748, or confirm your engine's model and serial range against the application data in the specs. Confirming the number is the surest way to get the correct impeller.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Should I keep a spare on board?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"If you cruise away from the ramp, it's smart. An impeller is inexpensive and compact, and swapping one at the dock is far easier than dealing with an overheated engine on the water.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"Sierra","offers":[{"title":"Default Title","offer_id":45078480224349,"sku":"2009883","price":24.09,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_03cdf162-c714-4589-b506-0d2e986ebf7f.jpg?v=1789935300","url":"https:\/\/nvnmarine.com\/products\/sierra-18-3012-impeller-for-mercury-outboards","provider":"NVN Marine","version":"1.0","type":"link"}