whats wrong with it
What kind of boat with what kind of power?
Sounds like your messed up your gears. Have a tech look at the gearcase, lower unit or transmission, depending upon whether you have a sterndrive, outboard or inboard.
Is the boat out of the water, or in now? Better check for leaks if you wet store.
Pull the cover off your transom and wiggle the shifter lever under it. Mine hung in gear and when I did this it broke loose.