Blue Sea M-Series Battery Switch On/Off with Key

The Blue Sea M-Series Battery Switch On/Off with Key is the marine electrical control standard trusted by commercial fishermen, serious cruisers, and weekend boaters who demand reliability in unforgiving saltwater environments. This keyed battery disconnect switch serves as both a master power control and anti-theft safeguard, allowing you to isolate all 12V DC circuits instantly—essential for equipment security, troubleshooting, and safe battery maintenance while docked or anchored. Whether you're running a center console, cabin cruiser, or fishing vessel, a quality battery switch is non-negotiable for engine protection and crew safety.

Built by Blue Sea Systems—a brand synonymous with marine-grade electrical integrity—this M-Series unit features tin-plated copper studs that resist corrosion and oxidation in salt spray and high-humidity conditions where ordinary brass would degrade rapidly. The studs accept standard 3/8" (M10) ring terminals and provide 7/8" (22mm) stud length, allowing multiple cable terminations per stud for consolidated wiring runs typical of modern vessel electrical architectures. The keyed design prevents accidental disconnection and unauthorized engine starts, a practical safeguard on rental or shared vessels and unattended watercraft.

This switch is compatible with any 12V DC marine electrical system and mounts directly to engine bulkheads, console frames, or accessible interior panels near the helm. Installation requires basic marine wiring skills and a crimper for ring terminals; consult your vessel's electrical schematic to ensure proper inline placement between the main battery bank and distribution bus. Weighting just 0.62 lbs, it installs cleanly without adding weight or clutter to tight engine compartments or helm stations where space is precious.