Sorry to read this. The forward tank is not ez to remove. Stern tank is much easier. Could be a tear or bad weld. Rip it out!
Ask for a saws all for Christmas.
When I got to this post in the discussion about it being the forward tank that failed, I knew it was, IMO, from the pounding of the sea being much more severe up aft than in the rear of the boat. IMO, it is Marlin's fault for putting a gas tank up in front of the CC (if I'm correct in assuming that's where it is).
I had a tank fail exactly like andybru in a 32 foot Wellcraft. I had it replaced but it was a $10,000 job, and just from checking in on the progress, it is not something anyone but a professional should even attempt.
After it was fixed, I sold the boat.
I currently own a 42 Performance, and I've put 1500 hours on it (owned it from new (2001) - two repowers) in some of the roughest seas one can imagine (long 100 mile trips often - out of sight of land) and the tank has not "ruptured".
My fuel tank is about 270 gallons 1/4 inch standard, and after ten years of use the area on top of the tank where the (4) pickups are started to corrode with tiny pin holes at first that leaked gasoline when I filled up. I called a local Bahamian "Tank" guy and he fiberglassed over the holes - and he sanded and sanded the AL tank to prep for the glass job for an area of 3 feet by three feet (from the pickups) - and I made him go half way up for added protection.
It stopped the problem, but I still won't fill the tank all the way to the top.
That's where a fuel tank will leak on you first, around the pickups … IMO. I asked a marine owner (Bobby Brown - Brown's boat yard, Nassau, Bahamas) whose been hauling and fixing boats since the beginning of WWII, and he said it's a common problem with older boats.
I wonder if there's a tank man out there that would like to comment, as I'd be interested in reading what he has to say. The fiberglass job has held up for 8 years, but I can see gasoline "seeping around" occasionally threw the glass - not comforting.
I would think a thick hard drying "tar" based paint would be good for the top of any fuel tank over 10 years old, but ask a professional - which I'm not.
Sirgrady above mentioned a "failed weld", and that's where they all leak and fail if you ask me. 1/4 inch AL is pretty tuff.
The boatbuilder who built my 42 Performance and at least 100 more just like it, says he buys his tanks from one manufacturer and he is very good.
Shop around and make sure you get the best 1/4 inch AL tank you can find.
Good luck to you, and Merry Christmas.