Water in our gas tank??? 

I just had to tear mine out recently..... But it lasted 33 years so can't complain much! Currently running an auxiliary tank. Good luck and hope everything is up and running soon!!

our old big bay had the exact same issue

I've used diamond-coated cutting wheels and sacrificial metal-cutting wheels on aluminum plate and the aluminum plugs up both types of wheel and cutting becomes real slow. The best cutter I've found is a wood-cutting blade turned backwards. Cuts real easy but is unbelievably loud.

The safest way I've found to weld and cut a tank is run a hose from an exhaust pipe till the tank is warm and cut away with torch or what ever you have. No oxygen no fire. This is not my idea' From a commercial welder that does it everyday.

I need do my tank as well I'm diggin that material on ya floor wats Name brand ?

Was it bay water or rain water from storing boat outside

Ouch

So I guess you were getting fuel in bilge?