{"product_id":"ignition-trigger-for-mercury-mariner-4-cylinder-outboards-1976-1997-interchanges-134-6452-sierra-18-99390","title":"Sierra Trigger 18-99390 for 4 Cylinder Mercury\/Mariner Outboards (1976-1997), Replaces 134-6452","description":"\u003cp\u003eThe Sierra 18-99390 is a replacement ignition trigger built for 4 cylinder Mercury and Mariner outboard engines produced between 1976 and 1997. The trigger is a core ignition timing component: it generates the signal that tells the ignition module precisely when to fire each cylinder, so a worn, cracked, or intermittently failing trigger is a common cause of misfires, rough idle, hard starting, or a complete no-spark condition on these engines.\u003c\/p\u003e\u003cp\u003eThis trigger cross-references directly to part number 134-6452, making it straightforward to confirm you are ordering the correct unit for your 4 cylinder Mercury\/Mariner powerhead. It is a compact assembly measuring 6 x 6 x 1.75 inches and weighing 0.5 pounds, sized to mount in the same location as the original trigger it replaces, underneath the flywheel on applicable 4 cylinder Mercury and Mariner outboards.\u003c\/p\u003e\u003cp\u003eBecause ignition timing accuracy directly affects starting reliability, smooth running, and fuel efficiency, replacing a failing trigger with a properly specified unit like the Sierra 18-99390 restores consistent spark timing rather than masking a deeper ignition fault.\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 18-99390\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Dimensions:\u003c\/strong\u003e 6 x 6 x 1.75 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 0.5 pounds\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUPC:\u003c\/strong\u003e 808282394233\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM Cross Reference:\u003c\/strong\u003e 134-6452\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEngine Application:\u003c\/strong\u003e 4 Cylinder\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFitment:\u003c\/strong\u003e Mercury\/Mariner outboards, 1976-1997\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eMercury outboards, 4 Cylinder, 1976-1997\u003c\/li\u003e\n\u003cli\u003eMariner outboards, 4 Cylinder, 1976-1997\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eReplaces (OEM)\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e134-6452\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat does the Sierra 18-99390 trigger fit?\u003c\/strong\u003e The Sierra 18-99390 trigger fits 4 cylinder Mercury and Mariner outboards built between 1976 and 1997.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the Sierra 18-99390 the same as part number 134-6452?\u003c\/strong\u003e Yes, 134-6452 is the cross-reference number for the Sierra 18-99390 trigger, so it installs and functions in place of that number.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow much does this trigger weigh?\u003c\/strong\u003e The Sierra 18-99390 trigger weighs 0.5 pounds.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat are the dimensions of the Sierra 18-99390 trigger?\u003c\/strong\u003e This trigger measures 6 x 6 x 1.75 inches.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill this trigger work on a 6 or 8 cylinder Mercury outboard?\u003c\/strong\u003e No, the Sierra 18-99390 is built specifically for 4 cylinder Mercury\/Mariner outboards from 1976 to 1997, not other cylinder counts.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes the Sierra 18-99390 fit both Mercury and Mariner outboards?\u003c\/strong\u003e Yes, this trigger fits 4 cylinder Mercury and Mariner outboards built between 1976 and 1997.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat UPC is assigned to this part?\u003c\/strong\u003e The Sierra 18-99390 trigger carries UPC 808282394233.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs the 18-99390 a genuine Sierra part or a generic aftermarket copy?\u003c\/strong\u003e The 18-99390 is a Sierra-branded replacement trigger that cross-references to OEM\/aftermarket number 134-6452.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat does a trigger actually do in the ignition system?\u003c\/strong\u003e A trigger generates the timing signal that tells the ignition module when to fire each cylinder, so a failing trigger like the one replaced by Sierra 18-99390 can cause misfires, hard starting, or no spark.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I install the Sierra 18-99390 trigger myself?\u003c\/strong\u003e Replacing the Sierra 18-99390 trigger is a standard ignition component swap that involves removing the flywheel to access the trigger assembly on 4 cylinder Mercury\/Mariner outboards.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat do I receive when I order this part?\u003c\/strong\u003e Ordering the Sierra 18-99390 gets you one replacement ignition trigger assembly for 4 cylinder Mercury\/Mariner outboards, 1976-1997.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Default Title","offer_id":48988443115739,"sku":"SIE-18-99390","price":115.28,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/CDI-134-6452_lg__65351.1558113037.500.750.jpg?v=1785188563","url":"https:\/\/www.goodvibesmarina.com\/products\/ignition-trigger-for-mercury-mariner-4-cylinder-outboards-1976-1997-interchanges-134-6452-sierra-18-99390","provider":"Good Vibes Marina","version":"1.0","type":"link"}