filler?
Should it be re-riveted, or welded?
The leak isn't real bad -maybe a gallon of water every 15-20
minutes (a wild guess). Its not gushing up through, but I also
would not want to be out on the water far from shore for any length of
time.

Any suggestions or recommendations would be very appreciated.

(I only paid $125 for the boat and motor.).

I had an 18' Al Grumman. Paid $50 for it. A bunch of cowboys had it for
a few years. not a rib left intact.

Construction adheasive on the inside will work. Drink a case of cheep
canned beer. You'll have the "repair" material needed.

Bob