[Bosts1]

my fuel gauge has recently started hanging on 3/4 full....i know this is not correct. I took out the fuel sending unit and played with it out of the tank and it works. but i put it back in the tank, and when i put gas in it, it went back to 3/4, and whether i run the boat or add gas it doesn't move?? What could it be???????? Thanks in advance!