Keep your bow line, untie your stern line and apply some power in reverse. Two things might happen. If the boat behaves to turn to port keep your rudder to port and keep going in reverse. Leave the pontoons in reverse. If the boat seems parallel to the slip, apply some power in reverse and maneuvre between the pontoons.
You might also wait for some time, with your bowline which will direct the boat to the wind. If prop walk is not too much, keep your rudder to starboard and leave te slip.