Overview

The Blue Sea Systems 7903 is a red spare locking key for compatible M-Series battery switches. It is the replacement key itself, not the switch assembly, so it is used when the original key is lost, damaged, or kept as a backup on board.

This part fits the keyed version of the Blue Sea Systems M-Series battery switch range, including the 6004 Single Circuit ON-OFF with locking key. It gives you back normal access to the switch without replacing the full battery switch body, which matters when the rest of the switch is still in good working order.

On a boat, a missing battery switch key can stop you from isolating a battery bank before storage, service, or electrical work. Keeping a spare like this aboard is a simple way to avoid that problem, especially on small powerboats, tenders, and sailboats using a keyed M-Series switch at the battery compartment or main DC disconnect point.

Key features

• Spare locking key for Blue Sea Systems M-Series battery switches that use a keyed handle
• Compatible with the keyed M-Series setup, including the 6004 Single Circuit ON-OFF battery switch
• Red key matches the red keyed M-Series switch version for straightforward identification
• Useful as a direct replacement for a lost key or as a backup kept on board
• Key-only service part for restoring access without replacing the complete battery switch

Compatibility and fit

This key is for the locking-key version of the M-Series switch, not the standard knob version and not a complete replacement lock set. Before ordering, check that your existing switch is a keyed M-Series model and that you need the spare key rather than the full switch or another service part.

Because this is a mechanical replacement key, it does not change the switch's electrical ratings or the way the battery switch is wired into the boat. Its job is simply to restore operation of a compatible keyed switch that is already installed.

Use on board

This is a sensible spare for owners who lock out battery power when leaving the boat, winterizing, or working on the DC system. It also suits technicians and service crews who want a replacement key on hand so a missing original key does not delay routine electrical work.