You will have to either
pump the tank dry through the deck fill or siphon the tank empty from the pickup tube. Then you can put the
fuel water mix into another container, let it seperate and then capture the gas into yet another container through a water seperating funnel. Put this into tank or better yet, into your friends car. Add a stabilizer such as STARBRITE StarTron to your boat tank and refill. That should deal with any residual water.
Have fun!