When I had to remove mine (throttle lever broke clean off at the base) I had to drill off the heads. Be careful not to drill through or break the base of the shifter plate. I am not sure of the year or your boat, but the screws on my boat went through the fiberglass and into a strip of aluminum that has been tapped to grip the screws. By the time I was able to back the seized screws with pliers I stripped the aluminum. I ended up re-tapping the aluminum plates up one size since I had to by new screws anyway.