{"product_id":"distributor-rotor-and-shaft-assembly-for-mercury-4-and-6-cylinder-outboards-sierra-18-99308-cdi-994-4371-interchange","title":"Sierra Rotor\/Shaft Assembly 18-99308 for 4\/6 Cylinder Outboard Engines","description":"\u003cp\u003eThe Sierra Rotor\/Shaft Assembly, part number 18-99308, is a replacement ignition rotor and shaft assembly built for 4 and 6 cylinder outboard engines. This component is a core part of the engine's ignition system, working with the distributor to route spark to the correct cylinder in firing order. As the engine's original rotor and shaft wear from heat cycling and continuous rotation, ignition timing accuracy and spark delivery can degrade, leading to misfires, hard starting, or rough idle. Replacing the rotor\/shaft assembly restores proper spark distribution and helps the ignition system perform as designed.\u003c\/p\u003e\u003cp\u003eThis assembly is compatible with ignition systems from CDI Electronics, giving boat owners and marine technicians a straightforward option when servicing 4 or 6 cylinder outboard ignition components. It is sized and configured specifically for 4\/6 cylinder applications, so it should be matched to the correct cylinder count before ordering.\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 18-99308\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Type:\u003c\/strong\u003e Rotor\/Shaft Assembly\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCylinder Configuration:\u003c\/strong\u003e 4\/6 Cylinder\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatible Ignition System:\u003c\/strong\u003e CDI Electronics\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.9 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 736983857217\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCategory:\u003c\/strong\u003e Mercury Outboard Parts\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cp\u003eFits 4 and 6 cylinder outboard engines.\u003c\/p\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat engines does the Sierra 18-99308 rotor\/shaft assembly fit?\u003c\/strong\u003e The Sierra 18-99308 is built for 4 and 6 cylinder outboard engines that use a distributor-based ignition system with a rotor and shaft.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat ignition system is the 18-99308 rotor\/shaft assembly compatible with?\u003c\/strong\u003e This rotor\/shaft assembly is compatible with CDI Electronics ignition systems used on 4\/6 cylinder outboard engines.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does part number 18-99308 weigh?\u003c\/strong\u003e The Sierra 18-99308 rotor\/shaft assembly weighs 0.9 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat does the rotor\/shaft assembly do in the ignition system?\u003c\/strong\u003e It rotates within the distributor to direct spark from the ignition coil to each spark plug in the correct firing order, so accurate rotor and shaft function is essential for proper engine timing.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat are the signs that a rotor\/shaft assembly needs to be replaced?\u003c\/strong\u003e Misfires, hard starting, rough idle, or inconsistent spark delivery can indicate a worn rotor and shaft, which is when a replacement like the Sierra 18-99308 is typically needed.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the 18-99308 a genuine Sierra part or an aftermarket copy?\u003c\/strong\u003e Part number 18-99308 is a Sierra branded rotor\/shaft assembly, sold under the Sierra part number as listed.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the 18-99308 rotor\/shaft assembly include the shaft as one piece with the rotor?\u003c\/strong\u003e Yes, the Sierra 18-99308 is a combined rotor\/shaft assembly, meaning the rotor and shaft are supplied together as a single unit.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan this rotor\/shaft assembly be used on both 4 cylinder and 6 cylinder outboards?\u003c\/strong\u003e Yes, the Sierra 18-99308 is designed for use on 4 and 6 cylinder outboard engine applications.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat category of outboard parts does the 18-99308 belong to?\u003c\/strong\u003e The Sierra 18-99308 rotor\/shaft assembly falls under Mercury outboard parts.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the UPC for the Sierra 18-99308 rotor\/shaft assembly?\u003c\/strong\u003e The UPC for the Sierra 18-99308 rotor\/shaft assembly is 736983857217.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988441444571,"sku":"SIE-18-99308","price":312.12,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/CDI-994-4371_lg__61960.1558115320.500.750.jpg?v=1785188257","url":"https:\/\/www.goodvibesmarina.com\/products\/distributor-rotor-and-shaft-assembly-for-mercury-4-and-6-cylinder-outboards-sierra-18-99308-cdi-994-4371-interchange","provider":"Good Vibes Marina","version":"1.0","type":"link"}