{"product_id":"sierra-18-3915-piston-ring-set-030-oversize-3-217-in-bore-for-evinrude-johnson-35-70-hp-2-3-cyl-outboards-replaces-omc-391416-434109","title":"Sierra Piston Rings 18-3915,.030 Oversize, 3.217 Bore, Evinrude 50-70 HP 3-Cylinder, Replaces 391416, 434109","description":"\u003cp\u003eThe Sierra 18-3915 piston ring set is built for the 3-cylinder, 50-70 HP outboard engine family with a 3.217 inch cylinder bore and a.030 inch oversize specification. Matching your engine's bore size and oversize is critical when rebuilding a powerhead, since installing the wrong ring size can lead to poor compression, oil consumption, or premature cylinder wear. This set is designed to be installed on the corresponding oversize piston during a top-end or full powerhead rebuild, restoring proper ring-to-cylinder-wall seal so the engine can rebuild compression and run efficiently.\u003c\/p\u003e\u003cp\u003eSierra manufactures replacement marine engine components to OEM specifications, and the 18-3915 is cross-referenced to the original equipment piston ring numbers 391416 and 434109, making it a direct fit for engines originally equipped with those parts. It is intended for use by rebuilders and marine technicians performing cylinder and piston service on qualifying 3-cylinder 50-70 HP outboards.\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 18-3915\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Name:\u003c\/strong\u003e Piston Rings\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEngine Application:\u003c\/strong\u003e 50-70 HP, 3-Cylinder\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCylinder Bore Size:\u003c\/strong\u003e 3.217 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOversize:\u003c\/strong\u003e.030 inch\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM Cross Reference:\u003c\/strong\u003e 391416, 434109\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.07 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePackage Dimensions:\u003c\/strong\u003e 0.63 x 3.06 x 3.06 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 030999542809\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e50-70 HP, 3-Cylinder outboard engines with a 3.217 inch cylinder bore,.030 inch oversize\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e391416\u003c\/li\u003e\n\u003cli\u003e434109\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat engine does the Sierra 18-3915 piston ring set fit?\u003c\/strong\u003e It fits 3-cylinder, 50-70 HP outboard engines with a 3.217 inch cylinder bore and a.030 inch oversize specification.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat OEM part numbers does 18-3915 replace?\u003c\/strong\u003e The Sierra 18-3915 is a direct cross-reference to OEM piston ring numbers 391416 and 434109.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs this a standard or oversize ring set?\u003c\/strong\u003e The 18-3915 is a.030 inch oversize ring set, matching a 3.217 inch cylinder bore rather than the standard bore diameter.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat are the package dimensions of the 18-3915 ring set?\u003c\/strong\u003e The Sierra 18-3915 piston rings measure 0.63 x 3.06 x 3.06 inches as packaged.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the 18-3915 piston ring set weigh?\u003c\/strong\u003e It weighs 0.07 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhen would I need to install oversize piston rings like the 18-3915?\u003c\/strong\u003e Oversize rings such as the 18-3915 are used after a cylinder has been bored out.030 inch over standard, typically during a powerhead rebuild to restore proper compression.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDo I need to replace the piston along with the 18-3915 rings?\u003c\/strong\u003e The 18-3915 ring set is sized to match a 3.217 inch bore,.030 oversize piston, so it should be installed on the corresponding oversize piston for that bore specification.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-3915 a genuine OEM part or aftermarket?\u003c\/strong\u003e The 18-3915 is manufactured by Sierra as a replacement part built to OEM specifications, cross-referenced to original equipment numbers 391416 and 434109.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is included when I order part number 18-3915?\u003c\/strong\u003e Ordering 18-3915 gets you the complete piston ring set for one 3.217 inch bore,.030 oversize cylinder on a 50-70 HP 3-cylinder outboard.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill the 18-3915 rings fit a standard-bore cylinder?\u003c\/strong\u003e No. The 18-3915 is specifically sized for a 3.217 inch bore at.030 inch over standard, not a standard-bore cylinder.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988170322139,"sku":"SIE-18-3915","price":34.59,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/18-3915__06071.1739458781.500.750.jpg?v=1785188064","url":"https:\/\/www.goodvibesmarina.com\/products\/sierra-18-3915-piston-ring-set-030-oversize-3-217-in-bore-for-evinrude-johnson-35-70-hp-2-3-cyl-outboards-replaces-omc-391416-434109","provider":"Good Vibes Marina","version":"1.0","type":"link"}