Help please!!!

Ok guys I am new to the forums here but I would really love some help. I was recently given a 12 foot aluminum jon boat for free that my buddy was going to trash. It has four holes in it. Two round holes and two cracks about four inches long. I somewhat patched them up with jb weld just for a quick fix. I took it out yesterday for the first time. The boat has no braces in the bottom (they got removed for some reason) so the bottom of the boat flexes ALOT and it is very unstable. When i step on the front of the boat one of the wholes cracked back open and leaked pretty bad. So my question is what can I do to add support to the boat? Aside from taking it to someone who can weld aluminum is there anything else I can do? Any help is greatly appreciated!! Thanks guys!