Ask a boat mechanic about it. Also, somebody here has probably run into this before with a car that has been sitting.
You can probably add the appropriate amount of fuel treatment that has "water elimination" as one of its functions, drive around pulling the boat on the trailer for a decent distance, making lots of turns and going over some bumps to slosh everything around enough to thoroughly mix things up, then see how the engine runs. Maybe even add 10 or so gallons of fresh gas near the beginning of your "slosh run."
Something like this:
Rislone/16.9 oz. gasoline fuel system treatment
Upper cylinder lubrication
Moisture reducers
Water elimination
Fuel stabilizer
Treats 22 gallons
Rislone/16.9 oz. gasoline fuel system treatment (4700) | Fuel Additive and Cleaner | AutoZone.com