Blue Sea Systems m-Series Single Circuit ON-OFF Battery Switch, Locking Key, 48V DC, 300A Continuous, IP66, 3/8 in Studs

Overview

The Blue Sea Systems m-Series Mini Battery Switch is a single-circuit ON-OFF battery switch with a locking key for controlling one battery feeding one load group on board. It is rated for 48V DC systems, with a 300A continuous rating, 500A intermittent rating, and 900A starting rating for 30 seconds, making it a practical fit for many outboard and small gasoline or diesel engine installations.

The switch uses tin-plated copper studs that accept 3/8" (M10) ring terminals, with a 7/8" (22 mm) stud length to help accommodate multiple cable terminals where the installation allows. An isolating rear cover protects the contacts, while breakout tabs let cables enter from different directions for cleaner routing in compact battery compartments, helm panels, or equipment lockers.

Key features

• Single Circuit ON-OFF switching for one battery connected to one load group.
• 300A continuous rating with 900A starting capacity for 30 seconds.
• Maximum voltage rating of 48V DC for common low-voltage marine electrical systems.
• Tin-plated copper studs help maintain conductivity and resist corrosion in damp marine spaces.
• 3/8" (M10) studs work with standard heavy-duty marine battery cable ring terminals.
• Locking key operation helps limit accidental or unauthorized switching.
• IP66 rating supports use in areas exposed to spray and washdown.
• Ignition protected and rated to ISO 8846, SAE J1171, UL 1107, and UL 1500.

Variants

This switch is offered in two color configurations. Both variants use the same single-circuit ON-OFF layout with a locking key, the same 48V DC maximum voltage rating, and the same current ratings.

The color change affects how the switch presents on the boat and how easily it matches nearby panels, battery labels, or existing Blue Sea Systems electrical hardware.

• 6004: Red. The red version gives the battery control point a traditional high-visibility look, which can help it stand out in a battery compartment or behind an access panel.
• 6004200: Black. The black version has a more subdued appearance for helm panels, equipment lockers, or installations where the switch needs to blend with surrounding hardware.

Installation and fit

The compact m-Series form factor works well where space is limited but the battery switch still needs to handle engine starting loads. The case supports surface, front panel, or rear panel mounting, so it can be fitted to a bulkhead, panel face, or protected enclosure depending on the layout of the boat.

Use properly sized marine battery cable and ring terminals for the load being carried. The 3/8" terminal studs should be torqued to 120 in-lb (13.56 Nm), and the rear cover should be positioned so the live contacts remain protected after installation.

Electrical and marine use

This is a manual battery isolation switch for straightforward ON-OFF control, not a battery combiner or selector switch. It is a good match for boats that need a clear way to disconnect one starting or house battery feed when leaving the vessel, working on the electrical system, or shutting down nonessential loads at the dock.

The IP66 rating, ignition protection, tin-plated copper studs, and stainless flange nuts make it suitable for the kind of damp, vibrating, and corrosion-prone spaces found on small powerboats, tenders, fishing boats, and compact cruising boats.