Plan B. After cleaning the scuzzy goo off of the bottom of the tank I found several corroded spots including a deep 3/4 of the way through the alloy corroded spot about 1/4 by 2 inches in the lowest part of the aft end of the tank. I guess I dodged a bullet. Thanks to our discussion my checking the tank saved me a bilge full of fuel halfway to Bermuda. Front Street Shipyard is welding me a new,thicker tank and we are coating it with zinc chromate. It will be about $1100.