{"product_id":"lower-main-seal-for-evinrude-johnson-outboards-replaces-omc-331103-sierra-18-8307-oil-seal","title":"Sierra 18-8307 Oil Seal, Lower Main Seal, Replaces OMC 331103","description":"\u003cp\u003eThe Sierra 18-8307 is an Oil Seal sold as a Lower Main Seal for outboard motor applications, built to seal the lower crankcase\/driveshaft area against oil loss and water intrusion. It is designed as a direct cross-reference replacement for OMC\/Evinrude-Johnson part number 331103, and Sierra states that each of its parts meets or exceeds the specification of the original equipment part it replaces. The seal is precision-sized with an outside diameter of 1.628 inches, a shaft size of 1.110 inches, and a width of 0.448 inches, so it seats and rides correctly against the shaft without leaking or binding. At 0.03 pounds, it is a compact, lightweight component intended for straightforward replacement during routine maintenance or teardown of the lower unit\/crankcase seal area rather than a full rebuild. The part falls under Evinrude outboard prop and driveshaft seal applications, making it relevant to technicians and boat owners servicing these outboard components. Because it is an exact-fit replacement seal rather than a universal part, matching the part number or the OMC\/Evinrude-Johnson cross-reference number is the reliable way to confirm it is correct for a given engine before installation.\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 18-8307\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Type:\u003c\/strong\u003e Oil Seal (Lower Main Seal)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutside Diameter:\u003c\/strong\u003e 1.628 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eShaft Size:\u003c\/strong\u003e 1.110 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWidth:\u003c\/strong\u003e 0.448 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.03 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eColor:\u003c\/strong\u003e white\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 808282244934\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM Cross Reference:\u003c\/strong\u003e OMC 331103\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication Category:\u003c\/strong\u003e Evinrude Outboard Prop and Driveshaft Seals\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cp\u003eSpecific engine make, horsepower, and year fitment are not listed for this part; confirm fit by matching the OEM cross-reference number 331103 to your engine's original seal.\u003c\/p\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e331103\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat is the Sierra 18-8307 used for?\u003c\/strong\u003e It is an Oil Seal sold as a Lower Main Seal, used to seal the lower crankcase\/driveshaft area of an outboard motor against oil and water leakage.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat OEM part number does the 18-8307 replace?\u003c\/strong\u003e Sierra 18-8307 cross-references to OMC\/Evinrude-Johnson part number 331103.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-8307 a genuine or aftermarket part?\u003c\/strong\u003e It is an aftermarket Sierra part, manufactured to meet or exceed the specification of the original OMC 331103 seal it replaces.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the outside diameter of the 18-8307 seal?\u003c\/strong\u003e The outside diameter is 1.628 inches.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat shaft size does the 18-8307 fit?\u003c\/strong\u003e This seal is sized for a 1.110 inch shaft.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow wide is the Sierra 18-8307 seal?\u003c\/strong\u003e The width of the 18-8307 is 0.448 inches.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the 18-8307 weigh?\u003c\/strong\u003e The Sierra 18-8307 weighs 0.03 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat color is the Sierra 18-8307 seal?\u003c\/strong\u003e The 18-8307 is white.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the 18-8307 fit a specific engine year or horsepower?\u003c\/strong\u003e No specific make, horsepower, or year range is listed for the 18-8307; fitment should be confirmed by matching the OMC\/Evinrude-Johnson 331103 cross-reference number to your engine.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat category of application is the 18-8307 intended for?\u003c\/strong\u003e The 18-8307 falls under Evinrude outboard prop and driveshaft seal applications.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow is the 18-8307 different from the OEM 331103 seal?\u003c\/strong\u003e Functionally it is a direct replacement for OMC\/Evinrude-Johnson 331103, dimensionally matched at 1.628 inch OD, 1.110 inch shaft size, and 0.448 inch width.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat comes in the box with the 18-8307?\u003c\/strong\u003e The Sierra 18-8307 is supplied as a single Lower Main Seal unit.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988433481947,"sku":"SIE-18-8307","price":29.24,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/18-8307__47058.1737825783.500.750.jpg?v=1785188809","url":"https:\/\/www.goodvibesmarina.com\/products\/lower-main-seal-for-evinrude-johnson-outboards-replaces-omc-331103-sierra-18-8307-oil-seal","provider":"Good Vibes Marina","version":"1.0","type":"link"}