A #2 pencil size hole

like a new pencil about 6 or 7 inches long !!!
Get a bolt that fits that hole, coat it with some 3m5200 and tighten it up.
For other holes or leaks we suggest that you re-buck the rivets and use gluvit on the rivets and seams. It is a penetrating epoxy designed for that.
For serious large holes get a piece of aluminum (fairly thick) something like a piece of an aluminum street sign (hint hint) coat it with gluvit and rivit it in place or use 3m5200.
Use only stainless steel bolts and aluminum rivets when working with an aluminum boat. Do not use regular steel or any pressure treated wood since they will react with the aluminum.