Well, since no one is helping, I'll give it a shot...
BTW, welcome to the forum.
If you have a lot of fuel in there, start by siphoning off the bulk of it, or have it pumped out. See if there's an access plate near the rear of the tank where you may have access to the tank. In my boat, there's an inspection plate on deck, and the fuel sender is right below it. Would be easy to pull the sender and pump any last drops of water/fuel out of there.
If you end up with a quart or two of water at the bottom you could add a couple of gallons of stove alcohol, mix and pump out as much as you can. That was an old trick we used years ago for water in the fuel. Alcohol mixes with water and gasoline, so it would burn thru the motor if there wasn't too much water.
Seems to me you have to remove the deck to get the tank out. But if it's had water sitting in it for years it may be worth pulling it for inspection/replacment. I believe those were aluminum tanks, and can perforate from corrosion.
Let us know how it goes!
