Explain why FILL gas tanks, please. Thanks. Thought empty was a good choice.
The fuel you buy at the pump these days likely has alcohol/methanol in it.
With the extra space in the tank, condensation forms very readily. You will have a water and corrosion issue.
With bare aluminum exposed to air, corrosion is likely to form.
Obviously if the boat won't be running for several months, empty is better, but a month or two, full is preferred.
GT