{"product_id":"sierra-18-3021-neoprene-water-pump-impeller","title":"Sierra 18-3021 Neoprene Water Pump Impeller","description":"\u003cp class=\"nvn-hero\"\u003eThe Sierra 18-3021 is a neoprene water pump impeller, 2-9\/16 inches across and 2 inches wide, sold as a single unit. It's the flexible rubber heart of your engine's raw water cooling pump, and it's the one part you never want to let fail out on the water. Keep a spare aboard.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eHere's the thing about your raw water pump: it lives or dies on a little rubber impeller, and this is that impeller. The Sierra 18-3021 measures 2-9\/16 inches in diameter and 2 inches wide, molded from neoprene, and it ships as a single unit. It spins inside your cooling pump, its flexible vanes sweeping seawater through the housing and pushing it up into the engine to carry away heat. No impeller, no cooling. It's that simple.\u003c\/p\u003e\n\u003cp\u003eNeoprene is the right material for this job, and there's a reason Sierra molds these vanes from it. It flexes thousands of times a minute without cracking, it shrugs off salt and oil, and it holds its shape at the temperatures a hardworking engine throws at it. But nothing rubber lasts forever. An impeller is a wear part. The vanes take a set, they harden, and eventually a blade tears off and disappears down your cooling passages. That's the day your temp alarm goes off in the worst possible place.\u003c\/p\u003e\n\u003cp\u003eSo treat this as scheduled maintenance, not a repair. A lot of us swap the impeller every season, or roughly every 200 hours, whichever comes first. If you run in brackish or sandy water, do it more often. The grit chews the vanes faster than clean offshore water does. And any time you've run the pump dry, even for a few seconds, pull the cover and look. Dry running is what kills these fastest. The vanes need water to stay cool and lubricated, and they'll glaze and cook in no time without it.\u003c\/p\u003e\n\u003cp\u003eChanging one is a job most boaters can do at the dock with hand tools. Pop the pump cover, note which way the vanes are curled, and work the old impeller out. If it fights you, two flat-blade screwdrivers or a pair of pliers on the hub will walk it off the shaft. Slide the new 18-3021 on with the vanes bent the same direction the old one was leaning. A smear of dish soap or glycerin on the vanes helps it seat and gives it lubrication for that first dry startup. Never use petroleum grease. It swells and destroys neoprene. Then button up the cover with a fresh gasket or O-ring and you're back in business.\u003c\/p\u003e\n\u003cp\u003eOne honest word on fitment: match the part. This is the 2-9\/16 inch by 2 inch neoprene impeller, Sierra part 18-3021. Impellers come in dozens of diameters, widths, spline counts, and vane profiles, and they are not interchangeable across pumps. Check your pump or your old impeller against these dimensions and the Sierra number before you order. If the size and part number line up, you're good. If they don't, it's the wrong impeller for your pump no matter how close it looks.\u003c\/p\u003e\n\u003cp\u003eAnd here's the advice every old salt gives and every new owner learns the hard way: buy two. Keep one spare in the spares box or the ditch bag, wrapped in its packaging so it doesn't take a set sitting on a shelf. An impeller failure isn't a limp-home problem. Your engine overheats fast with no cooling water, and a small bag of torn rubber can turn into a very expensive tow or a cracked head. For the price of this part, carrying a spare is the cheapest insurance on the boat.\u003c\/p\u003e\n\u003cp\u003eSierra builds these to meet or beat the original equipment impeller they replace, same as the rest of their pump and cooling line. It's honest, no-drama gear. You install it, it does its job quietly for a season, and you replace it before it ever gets the chance to let you down.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003eNeoprene vanes flex thousands of times a minute without cracking and resist salt, oil, and engine heat\u003c\/li\u003e\n  \u003cli\u003eMeasures 2-9\/16 inches in diameter by 2 inches wide, sized to the Sierra 18-3021 pump application\u003c\/li\u003e\n  \u003cli\u003eFlexible-vane design sweeps raw water through the pump to keep your engine cool\u003c\/li\u003e\n  \u003cli\u003eSold as a single impeller, so it's easy to keep a spare on board\u003c\/li\u003e\n  \u003cli\u003eSierra parts are built to meet or exceed the original equipment impeller they replace\u003c\/li\u003e\n  \u003cli\u003eStraightforward dock-side swap with basic hand tools\u003c\/li\u003e\n  \u003cli\u003eDirect replacement by Sierra part number 18-3021 and matching dimensions\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 is the Sierra 18-3021?\u003c\/summary\u003e\n    \u003cp\u003eIt's a neoprene water pump impeller, 2-9\/16 inches in diameter and 2 inches wide, sold as a single unit. It's the flexible rubber rotor inside your raw water cooling pump that moves seawater through the engine.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should I replace my impeller?\u003c\/summary\u003e\n    \u003cp\u003eTreat it as scheduled maintenance. A lot of boaters swap it every season or about every 200 hours, sooner if you run in sandy or brackish water or if you've ever run the pump dry.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat is the impeller made of?\u003c\/summary\u003e\n    \u003cp\u003eNeoprene. It flexes thousands of times a minute without cracking and stands up to salt, oil, and engine heat far better than plain rubber.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs this a single impeller or a multi-pack?\u003c\/summary\u003e\n    \u003cp\u003eIt's a single impeller. It's smart to order two so you always have a spare on the boat.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow do I know if this fits my pump?\u003c\/summary\u003e\n    \u003cp\u003eMatch the dimensions and the part number. This is the 2-9\/16 inch by 2 inch neoprene impeller, Sierra 18-3021. Impellers aren't interchangeable across pumps, so check your old impeller or pump against these numbers before ordering.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat lubricant should I use when installing it?\u003c\/summary\u003e\n    \u003cp\u003eDish soap or glycerin on the vanes. It helps the impeller seat and protects it during the first dry startup. Never use petroleum grease, it swells and ruins neoprene.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat happens if I run the pump dry?\u003c\/summary\u003e\n    \u003cp\u003eThe vanes overheat and glaze or tear because they rely on water for cooling and lubrication. If you've run dry even briefly, pull the cover and inspect the impeller.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhich way do the vanes go when I install it?\u003c\/summary\u003e\n    \u003cp\u003eInstall the new impeller with the vanes curled the same direction the old one was leaning, matching the pump's rotation. Note the direction before you pull the old one out.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDo I need a new gasket when I change the impeller?\u003c\/summary\u003e\n    \u003cp\u003eReplace the pump cover gasket or O-ring if it's worn. A fresh seal keeps the pump priming properly. Reuse the old one only if it's still soft and undamaged.\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 18-3021 Neoprene Water Pump Impeller\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBrand\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\u003e18-3021\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e808282146214\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\u003eImpeller Style\u003c\/th\u003e\n\u003ctd\u003eFlexible neoprene vane\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMaterial\u003c\/th\u003e\n\u003ctd\u003eNeoprene\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eOutside Diameter\u003c\/th\u003e\n\u003ctd\u003e2-9\/16 in\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eWidth\u003c\/th\u003e\n\u003ctd\u003e2 in\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eConfiguration\u003c\/th\u003e\n\u003ctd\u003eSingle\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eSold As\u003c\/th\u003e\n\u003ctd\u003eEach\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eKeystone Part Number\u003c\/th\u003e\n\u003ctd\u003eS5M183021\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 is the Sierra 18-3021?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's a neoprene water pump impeller, 2-9\/16 inches in diameter and 2 inches wide, sold as a single unit. It's the flexible rubber rotor inside your raw water cooling pump that moves seawater through the engine.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How often should I replace my impeller?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Treat it as scheduled maintenance. A lot of boaters swap it every season or about every 200 hours, sooner if you run in sandy or brackish water or if you've ever run the pump dry.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What is the impeller made of?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Neoprene. It flexes thousands of times a minute without cracking and stands up to salt, oil, and engine heat far better than plain rubber.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is this a single impeller or a multi-pack?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's a single impeller. It's smart to order two so you always have a spare on the boat.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How do I know if this fits my pump?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Match the dimensions and the part number. This is the 2-9\/16 inch by 2 inch neoprene impeller, Sierra 18-3021. Impellers aren't interchangeable across pumps, so check your old impeller or pump against these numbers before ordering.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What lubricant should I use when installing it?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Dish soap or glycerin on the vanes. It helps the impeller seat and protects it during the first dry startup. Never use petroleum grease, it swells and ruins neoprene.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What happens if I run the pump dry?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"The vanes overheat and glaze or tear because they rely on water for cooling and lubrication. If you've run dry even briefly, pull the cover and inspect the impeller.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Which way do the vanes go when I install it?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Install the new impeller with the vanes curled the same direction the old one was leaning, matching the pump's rotation. Note the direction before you pull the old one out.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Do I need a new gasket when I change the impeller?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Replace the pump cover gasket or O-ring if it's worn. A fresh seal keeps the pump priming properly. Reuse the old one only if it's still soft and undamaged.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"Sierra Marine","offers":[{"title":"Default Title","offer_id":45072345366621,"sku":"2009225","price":48.19,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_6b1a240a-872b-4060-9f10-cfa4b812a731.jpg?v=1789739829","url":"https:\/\/nvnmarine.com\/products\/sierra-18-3021-neoprene-water-pump-impeller","provider":"NVN Marine","version":"1.0","type":"link"}