[olddog]

The inrush current when the starter motor is first engaged is everything the battery can supply. If you have a 1000 amp battery it will pull all 1000 amp.

Once at steady state, turning the engine over, if it takes 5 Hp to spin the engine, it will pull over 300 amp. On a warm day, it may be less on cold day it can be much more.

The factory does not fuse the starter, for a reason. The battery is what limits the current. Your headed down a road of trying to improve something that needs no improvement. Your just going to cause yourself a heap of trouble for no good reason.

The switch you had was not up to the task. Either eliminate it or get one that is up to the task.