{"product_id":"heurofosh-817109a2-starter-solenoid-relay-for-mercury-40-250-hp-outboards-12v-direct-fit-corrosion-resistant","title":"Heurofosh 817109A2 Starter Solenoid Relay for Mercury 40–250 HP Outboards — 12V Direct-Fit, Corrosion-Resistant","description":"\u003cp\u003e\u003cstrong\u003eHeurofosh 817109A2 is a 12V starter solenoid relay built as a direct-fit replacement for Mercury 40–250 HP outboard engines, delivering secure battery-to-starter switching for dependable engine starts.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eWhen an outboard won’t crank, a failed starter solenoid is a common culprit. The Heurofosh 817109A2 is engineered to match OEM form and function for many Mercury engines and several aftermarket cross-references, letting you restore reliable starting without custom wiring or lengthy troubleshooting. This description explains fitment, connections, and installation details to help you confirm compatibility before purchase.\u003c\/p\u003e\n\n\u003ch3\u003eWhich engines and parts does this solenoid replace?\u003c\/h3\u003e\n\u003cp\u003eThe 817109A2 is designed to replace multiple Mercury part numbers and several aftermarket equivalents, covering a wide range of 3-, 4-, and 6-cylinder outboards. Use the part cross-references and horsepower range to confirm it matches your engine model year and configuration.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eReplaces: Mercury 89-817109A3, 89-817109A2, 89-817109A1\u003c\/li\u003e\n  \u003cli\u003eAftermarket cross-references: Sierra 18-5834, Arco SW109, Arrowhead SMR6010, J\u0026amp;N 240-22131, WAI 67-731\u003c\/li\u003e\n  \u003cli\u003eCompatible horsepower: 40, 50, 65, 75, 80, 90, 100, 115, 125, 135, 150, 175, 200, 225, 250 HP\u003c\/li\u003e\n  \u003cli\u003eFits Mercury 3-cylinder, 4-cylinder and 6-cylinder engine variants\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow are the electrical connections configured?\u003c\/h3\u003e\n\u003cp\u003eThe solenoid uses standard marine terminal sizes and an isolated base for straightforward replacement wiring. Terminals are arranged for battery, starter motor, ignition switch, and ground, minimizing the need for terminal adapters or splicing if your original used the same layout.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eMain power terminals: 5\/16-18 for battery and starter motor\u003c\/li\u003e\n  \u003cli\u003eControl and ground: 10-32 switch and ground terminals\u003c\/li\u003e\n  \u003cli\u003eIsolated base prevents chassis shorting and simplifies mounting\u003c\/li\u003e\n  \u003cli\u003eMounting hole spacing: 68 mm center-to-center for bolt compatibility\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat should I expect during installation and performance?\u003c\/h3\u003e\n\u003cp\u003eInstallation is typically a direct swap: unbolt the old solenoid, disconnect the terminals, and transfer wiring to the Heurofosh unit. The relay is built to handle marine starting loads, offering reliable contact closure and reduced risk of intermittent starting related to corroded or worn solenoid internals.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eDirect-fit mounting and common terminal sizes speed up replacement\u003c\/li\u003e\n  \u003cli\u003eRobust internal contacts designed for repeated high-current cycles\u003c\/li\u003e\n  \u003cli\u003eCorrosion-resistant finish suited for marine environments\u003c\/li\u003e\n  \u003cli\u003eCompatible with factory wiring harnesses on supported engines\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWill this solenoid work with my boat’s electrical system and safety features?\u003c\/h3\u003e\n\u003cp\u003eThis Heurofosh relay is intended for standard 12V marine starting systems and pairs with OEM safety switches and ignition interlocks when those components are already compatible with the original solenoid. It does not alter safety circuits; if your boat has additional load or unconventional accessories, verify total current demands before replacing.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eDesigned for 12-volt outboard starter circuits\u003c\/li\u003e\n  \u003cli\u003eMaintains existing safety and interlock connections when directly replaced\u003c\/li\u003e\n  \u003cli\u003eNot intended to upgrade alternator output or non-standard high-current accessories\u003c\/li\u003e\n  \u003cli\u003eCheck total starter current draw if aftermarket starters are installed\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for: The Heurofosh 817109A2 is for boat owners, mechanics, and marinas needing a cost-effective, OEM-compatible replacement starter solenoid for Mercury outboards from 40 to 250 HP. Choose this unit if you require correct terminal sizing, standard mounting spacing, and reliable contact performance without modifying your existing wiring harness. If your engine uses different terminal threads, nonstandard mounting, or has unusually high starting currents, consult a technician before ordering.\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 solenoid fit my Mercury 115 HP outboard?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes — the Heurofosh 817109A2 is compatible with Mercury engines from 40 to 250 HP, including 115 HP models, when original terminal and mounting specs match.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: What terminal threads does the relay use?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Main battery and motor terminals use 5\/16-18 threads; switch and ground use 10-32 threads.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"Heurofosh","offers":[{"title":"Default Title","offer_id":55163266826583,"sku":"B0DKH9K9QH","price":58.1,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1050\/1524\/7191\/files\/heurofosh-solenoid-front-view.jpg?v=1790342775","url":"https:\/\/britishgarage.co.uk\/products\/heurofosh-817109a2-starter-solenoid-relay-for-mercury-40-250-hp-outboards-12v-direct-fit-corrosion-resistant","provider":"British Garage","version":"1.0","type":"link"}