so i've lived with the fuel gauge not working for a while, just filled up before we went out. Today i decided to change the fuel sending unit and still no reading on the fuel gauge. Is it coming for the guages themselves to need replacing or are there connections under the dash that can become corroded over time and need some cleaning? How can i test if the fuel sending unit is working properly as well?

Make sure the sending unit body is grounded to the motor first. Then you can check the fuel sender with an ohm meter standard marine fuel senders use 35-240 ohm. So when full should read 35 ohm and when empty should read 240 ohm. You can test the gauge by grounding the wire that goes to the center of the fuel sender. Turn the key to on then touch the wire to a good known ground <font color="ff0000">NOTE!!! Remove the wire or turn off key before the gauge gets all the way to full or you can damage the gauge.</font> Also the wire might be bad, try running a temporary wire from the gauge to the sender.