[Jaydee]

As long as the main wire from the battery to the solenoid is insulated and bolted properly, it is unlikely to ever short out. As long as the cable is heavy duty enough that if the starter got jammed, it would just keep winding { therefore you turn of the isolator] or if it shorted, the battery woulod die, before the cable will catch fire. So therfore, you really only need a 100 amp main fuse to the entire system after the starter. And obviously smaller fuses to individual items. Slightly of the subject. I made a anti theft device on the principle of a short. I coiled a thin telephone cable inside a bacolite tube with small holes and wired through a hidden switch. So if someone hotwired the ignition, it would instantly short out the wire creating a lot of acrid smoke, enough to scare of the thief. It only drained about 2 amps and would go open circuit very quickly. Only too bad if you forget to turn it of. But you could wire it to a light on the dash.
JD