The one on the left does have a wire on the fuse block so it’s a spare. The one on the right is missing the fuse but has a red wire with a tag on it, what does the tag say and is there anything not working?
Says ACCY (accessories) on the red missing a fuse.
Not working is floor-deck lights, tachometer (rpm) and voltmeter.
Accessories is a spare, my boat has two of them. The lights should be connected to the courtesy light switch at the helm. If not working check that fuse then see if there is power at the switch and lastly at each light fixture. Tach and voltmeter are not fused only there power from the ignition switch but since that works the fuse is ok. Try cleaning the terminals on each gauge.
You would connect your accessory to the Accessory switch on the helm, which is pulling power from the DC block and the circuit is protected by the fuse. The length of the run and the draw of the device will dictate the size of the wire. The draw of the device dictates the size of the fuse.
You have one slot acting as a spare fuse holder with nothing connected to it. And another slot dedicated to the Accessory switch. There is no fuse, but there is no telling if something is connected to te Acc switch or not.
Fuse block
Linear Mode
