I'll get flack for this, but you can siphon some from the bottom. That's where all the water is. Do this in manageable batches (2 gallons at a time maybe). Let it separate. Take as much water as you can off the bottom and discard. You should now have only gas. Repeat drawing from the tank until you aren't getting water anymore. You can do what you want with the drawn out gas, I mix it in small batches with good gas. Disconnect fuel line from engine. Run fuel pump and direct fuel line into container to purge line of water. Again, repeat until you have no separation. Change your fuel filter. Caveats:
1. You may or may not have taken all the ethanol out of your fuel. This may lower your octane rating
2. If this was bad gas (old gas) to begin with, it will still be bad.
3. I would mix whatever's left with fresh gas
4. I would not use the remaining gas if there's a ton left. Most I would do is 1-2 gallons old: 5 gallons new
5. There's nothing scientific about any of the above
Maybe less flack than you think.
You started out on the right track when you drew out and let the gas and water separate.
Just pour the gas off the top and be sure not to let water slip un-noticed along the bottom as you pour. (don't slosh while you pour)pour nice and slow, steady and easy.
Also the gas on top should not be cloudy, if it is, its still contaminated... let it sit and settle. give it time to clear up. hours if needed.
Again don't go sloshing it around after its separated.
Not knowing the separation line you questioned earlier, tells me you haven't done this before.
The gas is on top... So the first thing your pickup tube draws out of tank is water on the bottom. You got to get the water out and keep it out.
Not sure if this is years condensation or sitting too much or if you got bad gas at the pump. RARE but it can happen.
I am careful pouring from jugs/fuel cans, as I have had water accumulate again on bottom or last bit of pour be water.
Ethanol just seems to draw water to me, I could be wrong. But I have encountered this enough that I am watchful of it.
You may fight this Demon a while until you get all or most of the water out.
Expect a few filters sacrificed in the mean time.
Not sure how your tank is set up or you access ability or if you're able to see in the tank.
I don't envy your task ahead, But there's worse and better to be done.