{"product_id":"bolewin-marine-ignition-coil-compatible-with-mercruiser-thunderbolt-iv-v-direct-fit-for-gm-v6-v8","title":"BOLEWIN Marine Ignition Coil Compatible with Mercruiser Thunderbolt IV\/V — Direct-Fit for GM V6 \u0026 V8","description":"\u003cp\u003e\u003cstrong\u003eBOLEWIN's marine ignition coil replaces Sierra 18-5438 and fits Mercruiser Thunderbolt IV \u0026amp; V ignition systems to restore crisp spark and reliable starts for GM V6 \u0026amp; V8 marine engines.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eThis aftermarket ignition coil is engineered as a direct-fit replacement for common OEM numbers (Sierra 18-5438, Mercruiser 392-7803A4\/392-805570A2, Crusader 37068\/R117004 and others). It is designed for boats using HEI Thunderbolt IV and V ignition systems and works with GM V-6 and V-8 marine engines. With durable construction and application-specific design, the BOLEWIN coil aims to simplify installation while providing a consistent ignition source for routine use and seasonal maintenance.\u003c\/p\u003e\n\n\u003ch3\u003eWill this coil fit my Mercruiser Thunderbolt IV or V ignition setup?\u003c\/h3\u003e\n\n\u003cp\u003eYes — the BOLEWIN coil is built to match the form and function of the listed OEM part numbers so it integrates into Thunderbolt IV and V systems. Before ordering, confirm your engine uses HEI Thunderbolt IV or V and compare mounting and connector types with the original coil.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eDirect replacements for Sierra 18-5438 and listed OEM numbers\u003c\/li\u003e\n  \u003cli\u003eFits GM V-6 and V-8 marine engines with HEI Thunderbolt IV\/V\u003c\/li\u003e\n  \u003cli\u003eApplication-specific mounting and terminal layout for straightforward swap\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow does this ignition coil improve boat starting and engine performance?\u003c\/h3\u003e\n\n\u003cp\u003eAn ignition coil transforms battery voltage into the high-voltage pulses the spark plugs need. Replacing a worn or damaged coil with this BOLEWIN unit restores the intended spark intensity and timing reliability, which helps smoother starts and steadier idling under load.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eReplaces weak or intermittent coils to reduce misfires\u003c\/li\u003e\n  \u003cli\u003eStable high-voltage output supports consistent combustion\u003c\/li\u003e\n  \u003cli\u003eDurable construction resists marine vibration and heat exposure\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat should I know about installation and compatibility checks?\u003c\/h3\u003e\n\n\u003cp\u003eInstallation is typically straightforward for anyone familiar with marine electrical systems. Remove the old coil, match the mounting holes and electrical terminals, and follow manufacturer torque and grounding recommendations. If unsure, consult a marine technician to verify connector types and routing.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eMatch OEM part numbers and physical dimensions before purchase\u003c\/li\u003e\n  \u003cli\u003eVerify correct terminal orientation for your distributor or ignition module\u003c\/li\u003e\n  \u003cli\u003eEnsure solid ground and corrosion-free connectors during installation\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat durability and quality features does the BOLEWIN coil offer?\u003c\/h3\u003e\n\n\u003cp\u003eThe BOLEWIN coil uses robust materials and a design tuned to marine operating conditions. It aims to withstand engine compartment heat, vibration, and intermittent moisture exposure while maintaining reliable electrical performance over typical service intervals.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eRugged housing resists vibration and mechanical wear\u003c\/li\u003e\n  \u003cli\u003eHigh-quality internal windings for stable high-voltage delivery\u003c\/li\u003e\n  \u003cli\u003eOEM-equivalent electrical and mechanical specifications for long life\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho this is for: BOLEWIN's marine ignition coil is intended for boat owners, mechanics, and fleet maintainers who need a dependable, direct-fit replacement for worn or failing ignition coils on GM V-6 and V-8 engines that use Mercruiser Thunderbolt IV or V HEI systems. It's a practical option for seasonal engine reconditioning, routine maintenance, or emergency on-water repairs when OEM parts are specified by part number.\u003c\/p\u003e\n\u003csection class=\"product-faq-snippet\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Does this coil replace Sierra 18-5438?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes. It’s designed as a direct replacement for Sierra 18-5438 and listed OEM numbers.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Is it compatible with GM V8 engines using Thunderbolt V?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes. It fits GM V-6 and V-8 engines equipped with Mercruiser Thunderbolt IV and V HEI ignition.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"BOLEWIN","offers":[{"title":"Default Title","offer_id":48085521760414,"sku":"B0BKG7DBT4","price":39.5,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/2041\/9486\/files\/bolewin-ignition-coil-front-view.jpg?v=1785871488","url":"https:\/\/northtrailauto.ca\/products\/bolewin-marine-ignition-coil-compatible-with-mercruiser-thunderbolt-iv-v-direct-fit-for-gm-v6-v8","provider":"North Trail Auto","version":"1.0","type":"link"}