If you are hooking it directly to the battery and the fuse is blowing something is wrong, either with your hook up or the GPS itself.
Well I think its probably just a shitty design for the power adapter. Probably the battery has so much amperage its forcing its way through the adapter, causing the fuse to blow. This happens when the gps isnt even plugged in, so the circuit shouldn't even be complete.
Anyways, I stole power off of the high beam, seems to work well:
Thanks to everyone for your advice.