{"product_id":"sierra-18-7111-o-ring-for-omc-sterndrive-cobra-replaces-omc-301824-0-197-id-x-0-113-width","title":"Sierra 18-7111 O-Ring for OMC Sterndrive and Cobra Sterndrive Crankcase Head, 0.197 Inch ID","description":"\u003cp\u003eThe Sierra 18-7111 is a rubber-based O-ring engineered for the crankcase head on OMC Sterndrive and Cobra Sterndrive engines. It seals against oil and coolant leaks at the crankcase head joint, helping maintain proper lubrication pressure and preventing contamination from water intrusion. Sized at 0.197 inch (5mm) inside diameter with a 0.113 inch (2.9mm) width, this is a small but critical sealing component that is easy to overlook during a rebuild but can cause persistent leaks or crankcase pressure loss if it is worn, hardened, or omitted.\u003c\/p\u003e\u003cp\u003eBuilt from a rubber-based compound for resistance to marine fuels, oils, and coolants, the 18-7111 O-ring is sold as a single piece and is intended to be replaced any time the crankcase head is removed or serviced, rather than reused. Keeping a few of these on hand is good practice for anyone performing routine maintenance or a full rebuild on a compatible OMC or Cobra sterndrive powerhead.\u003c\/p\u003e\u003ch3\u003eSpecifications\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBrand:\u003c\/strong\u003e Sierra\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer Part Number:\u003c\/strong\u003e 18-7111\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNominal Inside Diameter:\u003c\/strong\u003e 0.197 inch (5mm)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWidth:\u003c\/strong\u003e 0.113 inch (2.9mm)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Rubber-based compound\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.01 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnit Count:\u003c\/strong\u003e 1 Count\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 808282259594\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eOMC Sterndrive \/ Cobra Sterndrive, 4 hp, 1969-90\u003c\/li\u003e\n\u003cli\u003eOMC Sterndrive \/ Cobra Sterndrive, 5 thru 300 hp, 1957-90\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\u003cli\u003eOMC 301824\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat does the Sierra 18-7111 O-ring fit?\u003c\/strong\u003e The Sierra 18-7111 O-ring is designed for the crankcase head on OMC Sterndrive and Cobra Sterndrive engines, covering 4 hp models from 1969-90 and 5 thru 300 hp models from 1957-90.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat size is the 18-7111 O-ring?\u003c\/strong\u003e It has a nominal inside diameter of 0.197 inch (5mm) and a width of 0.113 inch (2.9mm).\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-7111 the same as OMC 301824?\u003c\/strong\u003e Yes, the Sierra 18-7111 O-ring is the equivalent replacement for OMC part number 301824.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat material is the 18-7111 O-ring made from?\u003c\/strong\u003e It is made from a rubber-based compound designed to seal against marine oils, fuels, and coolants.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow many O-rings come in a pack?\u003c\/strong\u003e The Sierra 18-7111 is sold as a single unit, one O-ring per pack.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhere on the engine does this O-ring install?\u003c\/strong\u003e This O-ring seals the crankcase head on compatible OMC Sterndrive and Cobra Sterndrive engines.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eShould the crankcase head O-ring be reused during a rebuild?\u003c\/strong\u003e No, the 18-7111 O-ring should be replaced with a new one any time the crankcase head is removed, rather than reusing the old seal.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the Sierra 18-7111 O-ring weigh?\u003c\/strong\u003e It weighs 0.01 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-7111 a genuine Sierra part or aftermarket?\u003c\/strong\u003e The 18-7111 is a Sierra-manufactured O-ring sold as a direct replacement for the OMC 301824 crankcase head seal, not a repackaged OEM part.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat symptoms indicate a failed crankcase head O-ring?\u003c\/strong\u003e Oil seepage or a loss of crankcase sealing pressure around the crankcase head is a common sign that the 18-7111 O-ring needs to be replaced.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the 18-7111 O-ring fit both 2-stroke and 4-stroke OMC engines?\u003c\/strong\u003e The listed fitment for the 18-7111 covers OMC Sterndrive and Cobra Sterndrive models from 4 hp (1969-90) and 5 thru 300 hp (1957-90); check your engine's hp and year against this range before ordering.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the UPC for the Sierra 18-7111 O-ring?\u003c\/strong\u003e The UPC for the Sierra 18-7111 crankcase head O-ring is 808282259594.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988363948251,"sku":"SIE-18-7111","price":1.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/18-7111__78930.1722496037.500.750.jpg?v=1785188197","url":"https:\/\/www.goodvibesmarina.com\/products\/sierra-18-7111-o-ring-for-omc-sterndrive-cobra-replaces-omc-301824-0-197-id-x-0-113-width","provider":"Good Vibes Marina","version":"1.0","type":"link"}