{"product_id":"bi-directional-water-pump-for-volvo-penta-mercruiser-sterndrive-8503991-3853850","title":"Bi-Directional Water Pump for Volvo Penta\/MerCruiser Sterndrive 8503991 3853850","description":"\u003ch2\u003eBi-Directional Water Pump – Fits MerCruiser V6\/V8 Small Block (Replaces 8503991)\u003c\/h2\u003e\n\u003cp\u003eThis engine-mounted, bi-directional water circulating pump is designed for a wide range of marine engines, including MerCruiser, Volvo Penta, OMC, and other brands using GM small block V6 and V8 engines. It ensures reliable coolant circulation for optimal engine temperature.\u003c\/p\u003e\n\u003cp\u003eThis component is a direct replacement for MerCruiser part numbers 8503991 and 8M0113734, Volvo Penta 3853850, Sierra 18-3599-1, and others, offering a precise fit for compatible models.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstallation:\u003c\/strong\u003e Engine mounted for secure, direct integration.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Features a durable cast steel housing with a stainless steel backing plate for corrosion resistance.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e Designed for both steel and composite timing chain covers.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003ePart Number Cross-Reference\u003c\/h2\u003e\n\u003cp\u003eUse this table to confirm equivalent part numbers across OEM and aftermarket brands.\u003c\/p\u003e\n\u003cdiv style=\"overflow-x: auto;\"\u003e\n\u003ctable\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\u003eMerCruiser\u003c\/td\u003e\n\u003ctd\u003e8503991 \/ 8M0113734\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolvo Penta\u003c\/td\u003e\n\u003ctd\u003e3853850\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSierra\u003c\/td\u003e\n\u003ctd\u003e18-3599-1 \/ 18-3599-2\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCrusader\u003c\/td\u003e\n\u003ctd\u003e20318 \/ 7142520\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePleasurecraft\u003c\/td\u003e\n\u003ctd\u003eRA057018\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003ch2\u003eCompatible Engine Models\u003c\/h2\u003e\n\u003cp\u003eConfirm your engine model\/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial\/model: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/serial-number-guide\/mercury-outboard-serial-number-guide\" rel=\"nofollow noopener\" target=\"_blank\"\u003eMercury Serial Number Guide\u003c\/a\u003e. You can also review exploded diagrams to verify part numbers: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/diagrams\/mercury-parts-catalog\" rel=\"nofollow noopener\" target=\"_blank\"\u003eMercury Parts Diagrams \u0026amp; Catalog\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp\u003eConfirm your engine model\/year in the table below.\u003c\/p\u003e\n\u003cdiv style=\"overflow-x: auto;\"\u003e\n\u003ctable\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\u003eMerCruiser\u003c\/td\u003e\n\u003ctd\u003e4.3L V6\u003c\/td\u003e\n\u003ctd\u003e140-200\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1963-2014\u003c\/td\u003e\n\u003ctd\u003e8503991\/8M0113734\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003eWill NOT fit 2007+ V6 4.3L engines without water bypass hole\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMerCruiser\u003c\/td\u003e\n\u003ctd\u003e5.0L V8\u003c\/td\u003e\n\u003ctd\u003e155-205\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1963-2014\u003c\/td\u003e\n\u003ctd\u003e8503991\/8M0113734\u003c\/td\u003e\n\u003ctd\u003eSmall block applications\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMerCruiser\u003c\/td\u003e\n\u003ctd\u003e5.7L V8\u003c\/td\u003e\n\u003ctd\u003e230-260\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1963-2014\u003c\/td\u003e\n\u003ctd\u003e8503991\/8M0113734\u003c\/td\u003e\n\u003ctd\u003eSmall block applications\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolvo Penta\u003c\/td\u003e\n\u003ctd\u003eGM 4.3L\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1973 and later\u003c\/td\u003e\n\u003ctd\u003e3853850\u003c\/td\u003e\n\u003ctd\u003eV6 engine\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolvo Penta\u003c\/td\u003e\n\u003ctd\u003eGM 5.0L\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1973 and later\u003c\/td\u003e\n\u003ctd\u003e3853850\u003c\/td\u003e\n\u003ctd\u003eSmall block V8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolvo Penta\u003c\/td\u003e\n\u003ctd\u003eGM 5.7L\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1973 and later\u003c\/td\u003e\n\u003ctd\u003e3853850\u003c\/td\u003e\n\u003ctd\u003eSmall block V8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolvo Penta\u003c\/td\u003e\n\u003ctd\u003eGM 6.2L\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1973 and later\u003c\/td\u003e\n\u003ctd\u003e3853850\u003c\/td\u003e\n\u003ctd\u003eSmall block V8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolvo Penta\u003c\/td\u003e\n\u003ctd\u003eGM 6.3L\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1973 and later\u003c\/td\u003e\n\u003ctd\u003e3853850\u003c\/td\u003e\n\u003ctd\u003eSmall block V8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOMC\u003c\/td\u003e\n\u003ctd\u003eV6\/V8 Small Block\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e1968-1998\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003eSmall block applications\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCrusader\u003c\/td\u003e\n\u003ctd\u003eSmall Block V6\/V8\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e20318, 7142520\u003c\/td\u003e\n\u003ctd\u003eSmall block applications\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIndmar\u003c\/td\u003e\n\u003ctd\u003eSmall Block V6\/V8\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003eSmall block applications\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePleasurecraft\u003c\/td\u003e\n\u003ctd\u003eSmall Block V6\/V8\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\u003e-\u003c\/td\u003e\n\u003ctd\u003eRA057018\u003c\/td\u003e\n\u003ctd\u003eSmall block applications\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eProduct Type\u003c\/td\u003e\n\u003ctd\u003eBi-Directional Water Circulating Pump\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInstallation\u003c\/td\u003e\n\u003ctd\u003eEngine mounted\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConnection\u003c\/td\u003e\n\u003ctd\u003eThreaded ports with brass fittings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eHousing Material\u003c\/td\u003e\n\u003ctd\u003eCast steel with stainless steel backing plate\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eHousing Color\u003c\/td\u003e\n\u003ctd\u003eBlack\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFitting Type\u003c\/td\u003e\n\u003ctd\u003eBrass fittings with hose connections\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003eVaries by manufacturer - JLM Marine offers lifetime warranty\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOther Technical Attributes\u003c\/td\u003e\n\u003ctd\u003eBi-directional flow, compatible with steel and composite timing chain covers\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch2\u003ePackage Contents\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1 x \u003cspan style=\"color: red;\"\u003eWater Circulation Pump (8503991\/8M0113734)\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eExplosion Diagram\u003c\/h2\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/3853850.png?v=1728429832\" alt=\"Explosion Diagram\" loading=\"lazy\"\u003e\u003c\/p\u003e\n\u003ch2\u003eInstallation Guide\u003c\/h2\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cstrong\u003eDisconnect Battery:\u003c\/strong\u003e Ensure the engine is off and disconnect the negative battery terminal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDrain Coolant:\u003c\/strong\u003e Place a catch pan under the engine and drain the cooling system.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLoosen Belt:\u003c\/strong\u003e Loosen the tensioner to remove the serpentine belt from the water pump pulley.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove Hoses:\u003c\/strong\u003e Carefully disconnect the inlet and outlet hoses from the water pump.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnbolt Old Pump:\u003c\/strong\u003e Remove the mounting bolts securing the old water pump to the engine block.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eClean Surface:\u003c\/strong\u003e Thoroughly clean the engine block's mounting surface to remove any old gasket material or sealant.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall New Pump:\u003c\/strong\u003e Position the new gasket and water pump onto the engine block and hand-tighten the bolts.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTorque Bolts:\u003c\/strong\u003e Tighten the mounting bolts to the manufacturer's recommended torque specifications.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReconnect Components:\u003c\/strong\u003e Reattach the hoses and reinstall the serpentine belt, ensuring proper tension.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRefill System:\u003c\/strong\u003e Fill the cooling system with the appropriate coolant mixture.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCheck for Leaks:\u003c\/strong\u003e Reconnect the battery, start the engine, and carefully check for any leaks around the pump and hoses.\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eHow do I confirm this fits my engine?\u003c\/strong\u003e\u003cbr\u003eThis pump is designed for a wide range of MerCruiser, Volvo Penta, and OMC engines. A critical exception is that it \u003cstrong\u003ewill NOT fit 2007 and newer MerCruiser V6 4.3L engines that lack a water bypass hole.\u003c\/strong\u003e Please verify your engine model, year, and part number against the compatibility tables above.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the signs of a failing water pump?\u003c\/strong\u003e\u003cbr\u003eCommon symptoms include coolant leaks from the pump itself, an engine that is overheating, a loose or noisy water pump pulley, or steam coming from the engine compartment.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat does \"bi-directional\" mean?\u003c\/strong\u003e\u003cbr\u003eA bi-directional pump can operate correctly regardless of the engine's rotational direction (clockwise or counter-clockwise), making it versatile for different engine setups.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eOEM vs. Aftermarket?\u003c\/strong\u003e\u003cbr\u003eThis listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow fast do you ship and how much does it cost?\u003c\/strong\u003e\u003cbr\u003eWe offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is your warranty and return policy?\u003c\/strong\u003e\u003cbr\u003eThis product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused \u0026amp; in original condition); please see our policy page or reach out for instructions.\u003c\/p\u003e\n\u003ch2\u003eImportant Notes\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eVerify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.\u003c\/li\u003e\n\u003cli\u003eThis product is an aftermarket replacement part and is not an OEM component.\u003c\/li\u003e\n\u003cli\u003eProfessional installation is recommended to ensure safety and optimal performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eWhy Choose JLM MARINE?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eQuality Assured:\u003c\/strong\u003e As a trusted manufacturer for over 20 years, we supply top marine brands globally.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast Global Shipping:\u003c\/strong\u003e Free delivery worldwide in 5–15 days.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDirect from Manufacturer:\u003c\/strong\u003e Competitive pricing without compromising quality.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"JLM Marine","offers":[{"title":"Default Title","offer_id":49587694207289,"sku":"21FP003","price":158.77,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/Bi-directional_Water_Pump_for_Volvo_Penta_43-63_L___18-3599-1_-_JLM_MARINE-8288303.jpg?v=1755742106","url":"https:\/\/jlmmarine.com\/products\/bi-directional-water-pump-for-volvo-penta-mercruiser-sterndrive-8503991-3853850","provider":"JLM Marine Boat Parts Limited","version":"1.0","type":"link"}