{"product_id":"sierra-18-70925-mercruiser-molded-cooling-hose","title":"Sierra 18-70925 MerCruiser Molded Cooling Hose","description":"\u003cp class=\"nvn-hero\"\u003eThe Sierra 18-70925 is a pre-formed molded cooling hose that runs from the thermostat cover to the port exhaust manifold on MerCruiser V6 and V8 sterndrive and inboard engines, 305 and 350 cubic inch. It's built from EPDM tubing with a synthetic knit reinforcement, molded to hold its bend so water flows freely and the install stays simple. OEM-quality fit, form, and function.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eWhen a cooling hose on your MerCruiser starts weeping at the thermostat cover, you don't want to fight a length of straight hose into a tight bend. That's exactly what the Sierra 18-70925 solves. It's a molded hose, pre-formed to the shape it needs on the engine, so it holds the correct curve from the thermostat cover down to the port exhaust manifold without kinking or collapsing. Water flows the way it should, and the install goes a lot faster.\u003c\/p\u003e\n\u003cp\u003eThis one fits MerCruiser stern drive and inboard engines running the V6 and V8 small blocks, 305 and 350 cubic inch. If you've got one of those classic MerCruiser powerplants, this is the short molded run that carries water between the thermostat housing and the port side manifold. Get the fitment right by confirming your engine model and year before you order, since the routing on these blocks changed a little over the production years.\u003c\/p\u003e\n\u003cp\u003eSierra builds these molded hoses from EPDM tubing with a synthetic knit reinforcement. That matters. EPDM handles the heat and the water chemistry well, and the knit reinforcement layer keeps the hose from ballooning or collapsing under the pressure and vacuum swings a running cooling system sees. It's the same construction approach the original hose uses, so you're not stepping down in quality to save a few bucks.\u003c\/p\u003e\n\u003cp\u003eIt works on both fresh water (closed) and raw water (open) cooling systems. On a raw-water boat, that hose is moving lake or sea water straight through the engine, so keeping it in good shape is part of keeping the whole cooling circuit healthy. On a fresh-water-cooled setup, it's carrying coolant through the closed loop. Either way, a molded hose that actually matches the bend is less likely to chafe or crack than a forced-in straight piece.\u003c\/p\u003e\n\u003cp\u003eHere's how we'd approach the swap. Pull the old hose and take a good look at the thermostat cover and manifold gasket surfaces. Scrape them clean and flat, because a rough or scaled surface is where a slow leak starts, and it'll show up within a few weeks if you rush it. Slide the new molded hose on dry to check the routing first. It should sit naturally in its curve with no tension pulling it off the barbs. Keep it clear of the exhaust manifold surface where you can, so you're not resting rubber against a hot casting. Then set your clamps snug but not crushing, and run the engine on a set of muffs to check for leaks before you splash.\u003c\/p\u003e\n\u003cp\u003eA cooling hose is a smart thing to knock out while you're already in there. If you're pulling the thermostat cover to replace a thermostat, or you're servicing the water pump impeller, doing the molded hose at the same time means you're not back in that cramped spot again next season. On saltwater boats especially, give the whole cooling side a look every year. Hoses, clamps, the impeller, the thermostat. They're cheap parts that prevent an overheat, and an overheat is never cheap.\u003c\/p\u003e\n\u003cp\u003eWho's this for? Anybody maintaining a MerCruiser V6 or V8 sterndrive or inboard who wants the correct-shape replacement instead of guessing with universal hose. It's a direct, OEM-quality molded piece. Who's it not for? If your engine isn't one of the 305 or 350 cubic inch MerCruiser blocks, or the hose you're chasing is a different run than the thermostat-cover-to-port-manifold leg, check the part number against your engine's cooling diagram first. Molded hoses are shape-specific, so the right number matters more here than it does with straight hose. When in doubt, pull your old hose off and match the bend and the barb sizes against this one before you order. That's the surest way to know you've got the right leg for your engine.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003eEPDM tubing with a synthetic knit reinforcement resists heat and holds its shape under cooling-system pressure and vacuum\u003c\/li\u003e\n  \u003cli\u003eMolded to a pre-formed bend, so it routes cleanly from the thermostat cover to the port manifold without kinking\u003c\/li\u003e\n  \u003cli\u003eFits MerCruiser V6 and V8 stern drive and inboard engines, 305 and 350 cubic inch displacement\u003c\/li\u003e\n  \u003cli\u003eConnects the thermostat cover to the port exhaust manifold, a direct-fit replacement leg\u003c\/li\u003e\n  \u003cli\u003eWorks on both fresh water (closed) and raw water (open) cooling systems\u003c\/li\u003e\n  \u003cli\u003eOEM-quality construction matched to the original hose in fit, form, and function\u003c\/li\u003e\n  \u003cli\u003eBlack EPDM rubber for a clean, factory-style look on the engine\u003c\/li\u003e\n  \u003cli\u003eFull-flow molded shape keeps water moving through the bend for consistent engine cooling\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 engines does the Sierra 18-70925 fit?\u003c\/summary\u003e\n    \u003cp\u003eIt fits MerCruiser stern drive and inboard engines with V6 and V8 small blocks, 305 and 350 cubic inch displacement. Always confirm your exact engine model and year against your cooling diagram before ordering, since routing changed over the years.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhere does this hose go on the engine?\u003c\/summary\u003e\n    \u003cp\u003eIt's the molded run between the thermostat cover and the port exhaust manifold. That's the specific leg it's shaped for, so it holds that bend naturally once it's on.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat is the hose made of?\u003c\/summary\u003e\n    \u003cp\u003eSierra molds these from EPDM tubing with a synthetic knit reinforcement layer. EPDM handles engine heat and water well, and the knit keeps the hose from ballooning or collapsing under pressure.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWill it work on a raw water cooled engine?\u003c\/summary\u003e\n    \u003cp\u003eYes. Sierra molded hoses are designed for both fresh water (closed) and raw water (open) cooling systems, so it works whether your engine draws lake or sea water directly or runs a closed coolant loop.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs this an OEM-quality part?\u003c\/summary\u003e\n    \u003cp\u003eSierra builds these to meet or exceed the original hose in fit, form, and function. It's designed as a direct OEM-style replacement, not a generic universal hose.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhy buy a molded hose instead of cutting straight hose to length?\u003c\/summary\u003e\n    \u003cp\u003eA molded hose is pre-formed to the exact bend it needs. Straight hose forced into a tight curve can kink, collapse, or chafe, which restricts flow and shortens its life. The molded shape flows full water and installs cleaner.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat should I check when I install it?\u003c\/summary\u003e\n    \u003cp\u003eScrape the thermostat cover and manifold gasket surfaces clean and flat first, since a rough surface is where leaks start. Dry-fit the hose to confirm routing, keep it clear of hot exhaust surfaces, then set your clamps snug and run the engine to check for leaks before you launch.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eShould I replace anything else at the same time?\u003c\/summary\u003e\n    \u003cp\u003eIt's smart to service the cooling side together. If you're already pulling the thermostat cover or the water pump impeller, doing the molded hose at the same time saves you from going back into that tight space next season.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should I inspect it?\u003c\/summary\u003e\n    \u003cp\u003eOn saltwater boats especially, look over the whole cooling circuit every year: hoses, clamps, impeller, and thermostat. Catching a tired hose early is a lot cheaper than an overheat.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eAre hose clamps or a gasket included?\u003c\/summary\u003e\n    \u003cp\u003eThis listing is for the molded hose itself. Clamps and any thermostat cover gasket are sold separately, so grab those too if your old ones are worn.\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 18-70925 Molded Cooling Hose, Black, Fits MerCruiser Stern Drive and Inboard V6\/V8 (305 and 350 CID) Engines, Thermostat Cover to Port Manifold\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\u003e18-70925\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e808282145910\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eColor\u003c\/th\u003e\n\u003ctd\u003eBlack\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePart Type\u003c\/th\u003e\n\u003ctd\u003eMolded Cooling Hose\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eTubing Material\u003c\/th\u003e\n\u003ctd\u003eEPDM\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eReinforcement\u003c\/th\u003e\n\u003ctd\u003eSynthetic Knit\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCooling System Compatibility\u003c\/th\u003e\n\u003ctd\u003eFresh Water or Raw Water\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCompatible Engines\u003c\/th\u003e\n\u003ctd\u003eMerCruiser Stern Drive and Inboard, V6 and V8, 305 and 350 Cubic Inch Displacement\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eApplication\u003c\/th\u003e\n\u003ctd\u003eThermostat Cover to Port Manifold\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eConstruction\u003c\/th\u003e\n\u003ctd\u003eMolded, Pre-Formed Bend\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eSold As\u003c\/th\u003e\n\u003ctd\u003eSingle Hose\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 engines does the Sierra 18-70925 fit?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It fits MerCruiser stern drive and inboard engines with V6 and V8 small blocks, 305 and 350 cubic inch displacement. Always confirm your exact engine model and year against your cooling diagram before ordering, since routing changed over the years.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Where does this hose go on the engine?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's the molded run between the thermostat cover and the port exhaust manifold. That's the specific leg it's shaped for, so it holds that bend naturally once it's on.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What is the hose made of?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Sierra molds these from EPDM tubing with a synthetic knit reinforcement layer. EPDM handles engine heat and water well, and the knit keeps the hose from ballooning or collapsing under pressure.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Will it work on a raw water cooled engine?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Yes. Sierra molded hoses are designed for both fresh water (closed) and raw water (open) cooling systems, so it works whether your engine draws lake or sea water directly or runs a closed coolant loop.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is this an OEM-quality part?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Sierra builds these to meet or exceed the original hose in fit, form, and function. It's designed as a direct OEM-style replacement, not a generic universal hose.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Why buy a molded hose instead of cutting straight hose to length?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"A molded hose is pre-formed to the exact bend it needs. Straight hose forced into a tight curve can kink, collapse, or chafe, which restricts flow and shortens its life. The molded shape flows full water and installs cleaner.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What should I check when I install it?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Scrape the thermostat cover and manifold gasket surfaces clean and flat first, since a rough surface is where leaks start. Dry-fit the hose to confirm routing, keep it clear of hot exhaust surfaces, then set your clamps snug and run the engine to check for leaks before you launch.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Should I replace anything else at the same time?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's smart to service the cooling side together. If you're already pulling the thermostat cover or the water pump impeller, doing the molded hose at the same time saves you from going back into that tight space next season.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How often should I inspect it?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"On saltwater boats especially, look over the whole cooling circuit every year: hoses, clamps, impeller, and thermostat. Catching a tired hose early is a lot cheaper than an overheat.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Are hose clamps or a gasket included?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"This listing is for the molded hose itself. Clamps and any thermostat cover gasket are sold separately, so grab those too if your old ones are worn.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"Sierra Marine","offers":[{"title":"Default Title","offer_id":45076444774493,"sku":"2009742","price":28.09,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_8a5f680d-f754-435a-9450-b11ec73be498.png?v=1789887661","url":"https:\/\/nvnmarine.com\/products\/sierra-18-70925-mercruiser-molded-cooling-hose","provider":"NVN Marine","version":"1.0","type":"link"}