Try using two oversize patches made from an aluminum can (carefully cleaned first) and glue one to the inside AND the other to the outside of your boat using Marine Tex epoxy. Use enough, and make sure the patch fits flat against the boat. By patching both inside and out, in the event of failure, it may only be one patch of the other, giving you enough warning of impending disaster so you can act quickly to effect additional patching. Keep Marine Tex on hand on all trips on the water in case of patch failure--it will quickly seal even if applied below the water line (so the package says). Good Luck!
L. M. Urban
August 2007