I know from welding alum. heads you will need to preheat the area to be welded. A big piece of alu. just sucks up the heat like a heat sink. You might try to heat up the area first before trying to repair.
John

Doug

My daughter has some bubble gum that she got trick or treating, if I talk nice to her and tell her your situation she would give you a couple of pieces. If that doesn't work it's sounds like we are going to have another aluma-tub funneral. My deepist condolences.

Daryl

Doug,
I have a little experience in this area, if you recall.     You won't find a boat repair place anywhere in the state that will tackle this, but a few well-placed calls to welding shops will do the trick.  You'll need to bring the boat in for them to assess the work, and they'll all have differing opinions/rates on what it will take. No single way is the "right way", just the one that's the best option within your budget.

The larger issue is that the aluminum around the crack has thinned and weakened.  Thus making it difficult to repair (there's not much aluminum to work with).  Worse yet, the repair may only be temporary if this isn't taken into consideration - tears will appear around the repair in no time.

The solution for my boat was to weld up the 2' rips in the hull, then reinforce the areas by tack-welding aluminum angle iron over the weld, extending well beyond it, and then sealing it into place with Sikaflex 292. 

The welder was very good and did not need to remove the foam.  He was slow, cautious, and methodical.  The foam melted around the holes he repaired, but the reinforcement made up for it.

As for the rivets - I went to a machine shop supply store and got some solid-core rivets and replaced every stinkin' leaking rivet (28 of them!), dabbing them in FAA approved aircraft sealant before installing them.

The end result?  It was a bullet-proof, leak-proof tank.  All for under $500.

Yep, remove the foam from around the area that is to be fixed.  You can replace the foam with a can of expandable foam that can be purchase at any hardware store.  As for toxic gases given off by foam.  Lets talk Hydrogen Cyanide gas.  Deadly stuff that when inhaled over time is acumulative.  Some thing I get tested for by annually as a firefighter.  Would you huff enough doing the work yourself  probabable not, but why risk it.

Mark

Doug,
  To everyones point, no easy way except:  On the old Tracker that took Phil Hudgens, Chris Sergeant and I to nearly every WBC tournament from 1994 to 2004, It leaked like a siv until, Chris tried getting welded, we tried, to Glenns point JB WELD, epoxys from ever maker and still was a constant battle.  It would dry up until the first BIG "molar rattling" wave and it started leaking again.  As far as safety goes, I never felt unsafe.  A bilge pump in working order and the fact that there is no lake we fish in Washington that you cant make it to shore in 30 seconds if you had to kept me calm.
  The problem with "our Tracker" was that the major leaks were around the rivets that would slide against the bunk rail on the trailer when loading and unloading the boat, tearing apart any repair we made.  Then  I found the SOLUTION!  I traded that boat in dry as a bone!  The quick and "annual fix", even under the bunks was "GUTTER TAPE"!  I have some in my work truck and you can get it in the gutter isle of Home Depot.  The stuff if made of nearly "bulletproof" rubber with an extremely sticky adhesive on one side.  It is about an 1/8" thick, it stretchs, molds to contours of the hull and is even aluminum colored on the exposed side.  At first, I thought the stuff would just peel off because of waves, shallow water stumps and so on, NOT!  Once you put it on, you cant get it off!  Give me a call and I'll help you out on this.  This stuff works, and I don't think you'll have $20 bucks into it when you're done.  BEEN THERE, SURVIVED THAT!

Thanks everyone for all the suggestions and help.  Mike Wolsky has hooked me up with a guy who builds aluminium boats and he has offered to repair the crack and fix the leaky rivets.  Mike is going to haul it up North for me.  I think that this should take care of the problem and shouldn't cost an arm and a leg.  If for hwatever reason it doesn't work out the gutter tape may be the next big winner.  I hope that I can get a new (to me) boat in the near future but my wife has made an ultimatum, her or a boat.  Seems aweful tempting most of the time but I try and do the right thing and hang with the "ol boat" for as long as possible.  Thanks again everyone.

Doug, talk to Russ.  Maybe he can get you a boat for your wife.....

Rich