Fusible link melted!

Hey guys. After hours of troubleshooting I figured out that my short was in my ignition switch. I replaced it and the car started and ran awhile but the same fuse blew again(I replaced the fusible link with a 12 ga fuse holder). I had a 20 amp fuse in it then I put a 25 amp fuse in it and so far it had done fine. Is the 25 amp fuse big enough? I thought that the fuse probably had a lot of current going through it because the battery was deader than a door nail