after a longer period of absence in this forum due to pleasant familiar circumstances (I have become a happy grandfather) and a lot of other activities I will post some comments to this theme that has been discussed with passion also in several German forums. There are guys who use fuses and others who refuse to do because they claim that a fuse will be an unreliable component.
First of all I must confess that I am a definite supporter of the application of fuses in the power supply distribution of the submarine and I will try to explain the reasons that are as convincing as the reasons for the application of fuses in your domestic electric installation.
The purpose of a fuse is to protect your circuitry from excessive overcurrents that may burn off your cabling and may cause even a fire. In general a fuse cannot serve as a component that is able to prevent damage to electronic devices as their internal components like transistors will be destroyed much quicker than the fuse. This is often misunderstood.
A fuse must be selected carefully and matched to the wire sizes so that the fuse will blow earlier than the cable will start to glow and burn off.
At least you should apply a central fuse just in series to one of the battery terminals so the extreme current in case of a short within your circuitry will be interrupted just close to the power source. Keep in mind that without fuses a burning cable could even set your car or your house on fire!
Some modellers complain that fuse holders will be a source of trouble due to contact problems so they refuse the use of fuses. But such contact problems can be avoided basically by soldering the fuse to the wires that shall be protected. I use these flat fuse inserts you will find in many modern cars and solder the wire ends to the flat tabs of the fuse and isolate them with shrinking sleeves. This have been proved safe and reliable for many years (now 20 years for my older model of the German class 206A). You can get these fuses in many ratings (e.g. 3A, 5A, 10A, 15A, 20A, 25A, 30A) and their time behavior is relative slow blowing so that they can withstand short pulses of overcurrents.