Not clear why you think it's a good idea to drain the tanks.
I have a fuel transfer setup made from a automotive fuel pump. Hoses and a long wire wired to a lighter plug. I disconnect the primer bulb and hook up there.
This setup will get you most of the way there. As SEASICK said it's getting the last bit out that is difficult.
Be careful using the fuel in your car or truck. They have small fuel filters and may even be in your tank. If you crap one of those up or an injector it will be a expensive way to get rid of the fuel.
My advice would be to get as much out as you can with a pump. Treat the balance. In the spring fill tanks up and keep a close eye on the primary and secondary filters. Keep draining them until the fuel cleans up. You have to take the boat out and run it to get the water stirred up and have the filter pick it up. My boat sits all summer in NJ. When I take it to FL in the winter this is what I do.
I have had water in fuel problems is the past. Phase separation, water in fuel from fill o-rings. As much as I wanted to start fresh nobody want's the fuel. I haven't found anyone at any price. Best advise is to dilute with new fuel and burn it! Monitor your filters carefully. It's possible you could flame out both engines so bring everything you need to drop filter cans and re-fill with clean fuel.
This is what came out first trip. Afterwards everything was fine.
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