{"product_id":"mercury-mercruiser-screw-10-55300","title":"Mercury MerCruiser Quicksilver Screw 10-55300 (5\/16\"-18 × 5.250\")","description":"\u003ch2\u003eMercury Quicksilver Screw 10-55300 – 5\/16”-18 × 5.250”\u003c\/h2\u003e\n\n\u003cp\u003eThis is a genuine OEM Mercury Marine \/ Quicksilver structural screw used in MerCruiser engine and sterndrive assemblies. At 5.250 inches long with a 5\/16”-18 UNC thread, this is a long-reach fastener suited to deep-stack assemblies such as exhaust manifolds, risers, engine mounts, or gimbal housing positions where standard-length screws cannot reach. Always confirm the correct diagram position using your engine model and serial number before ordering.\u003c\/p\u003e\n\n\u003chr\u003e\n\n\u003ch2\u003ePart Details\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e 10-55300 (also referenced as 55300)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBrand:\u003c\/strong\u003e Mercury Marine \/ Quicksilver\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOfficial Product Type:\u003c\/strong\u003e Screw \/ Structural Fastener\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eThread:\u003c\/strong\u003e 5\/16”-18 UNC (0.312” diameter, 18 threads per inch)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLength:\u003c\/strong\u003e 5.250 inches\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSystem:\u003c\/strong\u003e Engine or drive assembly fastening — confirm diagram position for your application\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCondition:\u003c\/strong\u003e New OEM\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003chr\u003e\n\n\u003ch2\u003eCompatible Applications\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eMerCruiser engine assemblies requiring a 5\/16”-18 × 5.250” screw — specific position varies by model and serial number range\u003c\/li\u003e\n  \u003cli\u003eCommonly used in deep-stack fastening positions: exhaust manifolds, risers, engine mounts, or housing assemblies\u003c\/li\u003e\n  \u003cli\u003eVerify fitment using the Mercury parts diagram, engine model, and serial number before ordering\u003c\/li\u003e\n  \u003cli\u003eMatch thread pitch, diameter, and length exactly — do not substitute a shorter or longer screw in a structural position\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003chr\u003e\n\n\u003ch2\u003eDimensions\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eThread diameter:\u003c\/strong\u003e 0.312 in (5\/16”)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eThread pitch:\u003c\/strong\u003e 18 TPI (UNC coarse thread)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLength:\u003c\/strong\u003e 5.250 in (133.4 mm)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eApproximate weight:\u003c\/strong\u003e 80 g (0.08 kg)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003chr\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify thread specification and length against the parts diagram before installation\u003c\/li\u003e\n  \u003cli\u003eInspect threads in the mating component — chase or repair threads if necessary before installing a new screw\u003c\/li\u003e\n  \u003cli\u003eFollow Mercury service manual torque specifications — long screws in deep assemblies are prone to over-tightening\u003c\/li\u003e\n  \u003cli\u003eApply thread sealant or anti-seize only where specified by the Mercury service manual\u003c\/li\u003e\n  \u003cli\u003eReplace any screw showing corrosion, thread damage, or stretch deformation\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003chr\u003e\n\n\u003ch2\u003eService Interval\u003c\/h2\u003e\n\u003cp\u003eInspect fasteners whenever the assembly is disassembled for service. Replace any screw that shows corrosion, thread damage, or deformation. Mercury recommends replacing structural fasteners disturbed during major disassembly rather than reusing them in critical load-bearing positions.\u003c\/p\u003e\n\n\u003chr\u003e\n\n\u003ch2\u003eParts Desk Insights\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eBest use case:\u003c\/strong\u003e Replacement of a corroded or damaged long-reach structural screw in a deep-stack engine or drive assembly. The 5.250” length is specific — this screw is used where a standard 1” or 2” fastener cannot reach the mating thread, so having the correct length on hand before disassembly avoids delays mid-job.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCommon mistakes:\u003c\/strong\u003e Substituting a shorter screw because it threads in — a screw that doesn’t engage the full thread depth in a structural position will loosen under vibration and can cause assembly failure. Also confirm the thread is UNC (coarse, 18 TPI) and not UNF (fine thread): both 5\/16” diameters exist in Mercury assemblies and the threads are not interchangeable. Always torque to the Mercury service manual specification, not a generic fastener chart.\u003c\/p\u003e\n\n\u003chr\u003e\n\n\u003ch2\u003eRelated Parts\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/mercury-exhaust-riser-screw-43749\"\u003eMercury Exhaust Riser Screw 43749\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/mercury-quicksilver-hex-head-cap-screw-10-34353-3-8-16-x-1-oem-mercruiser-engine-fastener\"\u003eMercury Quicksilver Hex Head Cap Screw 10-34353 (3\/8”-16 × 1”)\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/mercury-mercruiser-transom-plate-mounting-screw-8m0215010\"\u003eMercury MerCruiser Transom Plate Mounting Screw 8M0215010\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/mercury-mercruiser-screw-10-53576-5-pack\"\u003eMercury MerCruiser Screw 10-53576 (Pack of 5)\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/mercury-quicksilver-washer-20583\"\u003eMercury Quicksilver Washer 20583\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/quicksilver-washer-26825-328-x-750-x-060-in-mercury-mercruiser-oem\"\u003eQuicksilver Washer 26825 (.328 × .750 × .060 in.)\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"MERC","offers":[{"title":"Default Title","offer_id":43563862687780,"sku":"55300","price":25.79,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0743\/5799\/7604\/files\/ca8c9aaa-c15a-45d8-a246-b101f121c896.png?v=1787268258","url":"https:\/\/marisolmarine.com\/products\/mercury-mercruiser-screw-10-55300","provider":"Marisol Marine Company","version":"1.0","type":"link"}