Hi As being a retired college welding teacher (33 yrs), I have several do’s and don’ts. 1. Is there any welding anywhere on that boat, if there is, then it should be ok to weld that hull.. 2. Being there is a crack next to that welded area, that indicates a NO WELD option. Alloys in the aluminum allow it to be heat treated, then tempered to increase the strength of the metal. Welding that heat treated aluminum destroys the alloys and heat treatment. In turn, that causes cracks a-long side the welds.. If there are any rivets anywhere on the boat, don’t weld, only patch with rivets.. Good luck