Fuse question

[firemanfitz]

I have a wire that is hooked into my number 2 battery switch which is then hooked to an inline 15 amp fuse which goes directly to my main fuse box in my cuddy that has a 5 amp fuse there. The wire goes nowhere else except from my battery switch to the fuse box. Not sure what that wire does or why it has two different size fuses. Do you think it is for my battery switch so it doesn't fry during an surge and if so why the two different size fuses. Hopefully this isn't a stupid question. Thanks

 

[UncleWillie]

Fuses are sized to protect the wiring.

The 15 amp fuse, (Which has likely has been replaced and should be 30 amps or more depending on the wire size), protects the wire from the battery to the fuse block. The 5 amp fuse protects the wire from the fuse block to the electrical device it powers.
Neither have anything to do with your battery switch.

 

[firemanfitz]

the wire with the 15 amp inline is actually hooked to my "feeder" post in my battery switch. On the fuse block where the 5 amp is it doesnt have a description on it telling me what it powers? The wire just goes from battery switch to a 5 amp terminal on block. There is no other wire leading to a accessory/device? Shouldn't it lead to a device? Hopefully I am making sense

 

[UncleWillie]

The 15 amp to the "Feeder" makes perfect sense.
The 5 amp used to power something that is no longer there and the fuse was just abandoned.
How many fuses will your fuse block accept? 6? 12?
What gauge wire is used for the Feeder Line and Ground lines. 10awg? 14awg?
It appears an extra fuse block was added and is no longer being used. Always a good thing to have though.