Sealing up a boat question

Hey guys,

I've got this old Aluminum boat and I'm trying to fix the small leaks and
cracks but their several. Is there a product that any of you know of that I
can just brush or roll on the bottom of the boat to seal it up? I thought
about having it Rhino Lined but that's a little more money than I want to
spend. They told me it would around 250 or so and the boats old enough, it
wouldn't be worth it I think.

Any ideas or suggestions would be appreciated.

Doug