Fuel Gauge Help

[Jonathan Allen]

I took the boat out today for the first time in about a month and noticed that the gas gauge was not working. I figured it went out becuase it was old so i went out and bought a new one. But after i hooked the new one up it still didnt work. My switch for my bow lights control the lights on the gauges also, all other gauges work, as well as the bow light when i flip the switch. None of my gauge lights work though. When i hit the light switch my gas gauge goes from empty to all the way full and back to empty when turned off. Anyone have any ideas as to what can be causing this. My dad said it may be the fuel sender but just wanted yalls opinion before i bought a new one