{"product_id":"marine-power-pack-for-johnson-evinrude-50-55-hp-2-cyl-1971-1977-replaces-oem-581397-sierra-18-99178","title":"Sierra 18-99178 Power Pack for Johnson\/Evinrude 50 HP and 55 HP 2-Cylinder Engines (1971-1977)","description":"\u003cp\u003eThe Sierra 18-99178 Power Pack is an electronic ignition module built to replace the original power pack on Johnson and Evinrude 2-cylinder outboard engines rated 50 HP and 55 HP from 1971-1977. The power pack controls ignition timing and spark delivery for the engine's 2-cylinder ignition system, and is a direct functional replacement for the original equipment module used on these outboards.\u003c\/p\u003e\u003cp\u003eConstructed with a plastic housing to protect the internal electronics from the marine environment, the 18-99178 mounts using an engine mount configuration and is designed as a straightforward swap for the factory unit on compatible 90 cubic inch displacement gasoline 2-cylinder Johnson\/Evinrude powerheads. It operates automatically once installed, requiring no manual adjustment during normal operation.\u003c\/p\u003e\u003cp\u003eThis power pack is intended for boat owners and marine technicians replacing a failed or aging ignition module on 1971-1977 Johnson\/Evinrude 50 HP and 55 HP 2-cylinder outboards, restoring reliable starting and consistent ignition timing.\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 18-99178\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Type:\u003c\/strong\u003e Power Pack\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatible Engine Brand:\u003c\/strong\u003e Johnson\/Evinrude\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCylinder Count:\u003c\/strong\u003e 2 Cylinder\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHorsepower Rating:\u003c\/strong\u003e 50 HP and 55 HP\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eModel Years:\u003c\/strong\u003e 1971-1977\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEngine Displacement:\u003c\/strong\u003e 90 Cubic Inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFuel Type:\u003c\/strong\u003e Gasoline\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Plastic\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eColor:\u003c\/strong\u003e Multicoloured\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMounting Type:\u003c\/strong\u003e Engine Mount\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.7 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM Cross Reference:\u003c\/strong\u003e 581397, 764708, 18-5755\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\u003cli\u003eJohnson\/Evinrude 2-cylinder engines, 50 HP and 55 HP, 1971-1977\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e581397\u003c\/li\u003e\n\u003cli\u003e764708\u003c\/li\u003e\n\u003cli\u003e18-5755\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat engines does the Sierra 18-99178 power pack fit?\u003c\/strong\u003e The Sierra 18-99178 fits Johnson\/Evinrude 2-cylinder outboard engines rated 50 HP and 55 HP from 1971-1977.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat OEM part numbers does 18-99178 replace?\u003c\/strong\u003e This power pack replaces OEM numbers 581397, 764708, and 18-5755.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does the 18-99178 power pack weigh?\u003c\/strong\u003e The Sierra 18-99178 power pack weighs 0.7 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat material is the power pack housing made from?\u003c\/strong\u003e The housing is made of plastic, providing protection for the internal ignition electronics.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes this power pack work with 3-cylinder or 4-cylinder Johnson\/Evinrude engines?\u003c\/strong\u003e No. The Sierra 18-99178 is designed specifically for 2-cylinder Johnson\/Evinrude engines rated 50 HP and 55 HP; it is not intended for engines with a different cylinder count.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow is the 18-99178 power pack mounted?\u003c\/strong\u003e It uses an engine mount configuration, matching the mounting setup of the original factory power pack it replaces.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the 18-99178 a direct replacement for the original power pack?\u003c\/strong\u003e Yes, the Sierra 18-99178 is built as a direct functional replacement for the factory power pack on compatible 1971-1977 Johnson\/Evinrude 50 HP and 55 HP 2-cylinder engines.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat fuel type is this power pack designed for?\u003c\/strong\u003e The 18-99178 is designed for gasoline-fueled 2-cylinder Johnson\/Evinrude outboard engines.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the power pack require manual adjustment after installation?\u003c\/strong\u003e No, once installed the 18-99178 operates automatically to control ignition timing without manual adjustment.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the engine displacement this power pack is designed for?\u003c\/strong\u003e It is designed for 90 cubic inch displacement Johnson\/Evinrude 2-cylinder engines.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use part number 18-5755 to cross-reference this power pack?\u003c\/strong\u003e Yes, 18-5755 is one of the OEM numbers the Sierra 18-99178 replaces, along with 581397 and 764708.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988438331611,"sku":"SIE-18-99178","price":144.89,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/CDI-113-1397_lg__16348.1558113355.500.750.jpg?v=1785188608","url":"https:\/\/www.goodvibesmarina.com\/products\/marine-power-pack-for-johnson-evinrude-50-55-hp-2-cyl-1971-1977-replaces-oem-581397-sierra-18-99178","provider":"Good Vibes Marina","version":"1.0","type":"link"}