Fuel gauge problem on 06 yamaha 4 stroke

[simonmd86]

I recently purchased a boat with a yamaha 60hp 4 stroke, the fuel gauge worked for the first couple of trips but now constantly shows the digital fuel gauge as being full, regardless of the amount of fuel i have. i ran the tank empty the other day and it still reads full. i pulled the sensor out of the tank and everything seems to be moving fine, e.g the sensor arm. i have no idea whats going on. please help :confused

[boats.net]

Most of the time it's a bad fuel sender.