I recently repaired a rip and in a 14 Aluminum V-Hull boat using a propane torch and Alumaweld. It worked fairly well but then I had to apply fiberglass to the bottom of the boat and allow it to run into the seams to reseal them because the heat from the propane melted the Alumalast that the factory uses to seal seams.
I also repaired a hole by making a patch from aluminum and using some Attwood Marine Sealant and bolting the patch in place with stainless steel nuts and bolts. This worked very well in my aluminum boat and it is still leakfree going on 2 years now. You might want to try this rather than welding, the Attwood Marine Sealant is a permanent repair if you use the permanent type and it only costs about $8 a tube.