If its blowing a 7amp it will prob blow an 8amp and even a 10amp too. It must be a short or bad part somewhere. Ask yourself this, if your house fuse was blowing would you stick in a larger one to temp get the power on? Or would you get it all checked out 1st?
Try an 8-10amp if u got one, a couple of amps shouldnt damage any wiring etc but dont go much over the size its meant to be cos otherwise it may not blow and burn out something. Fuses are rated for a reason afterall.
May be a bad sender or short in the fuel gauge electrics causing it to blow. You could take off the wires for it at the sender and temp tape them up to see if that helps and stops blowing fuses?
