Does anyone have any info on how to check to see if the float is stuck,or if there is a sending unit ? When I turn the key on the needle on the gauge moves from the left to empty and stops. So I assume it is getting a signal. It is a Gaffrig gauge and the boat is an 02 PowerQuest. Thanks for any help...

Is it one of those guage senders that has to be calibrated for empty and full? Check the website and look again at the wiring and install tech data. Thier's is different than most with a wire from ignition post on key to gu

You could stick a spare float (aka sending unit) on the sender input of the gauge and see what happens when you change the resistance (move it).

I have had two boats with problems in this area.

Both required a new float/sending unit to fix.

Never was the gauge.

Resistance is

33 ohms full
240 ohms empty

A loose wire will cause this. Put a jumper across the sender signal wire to ground BRIEFLY. If it jumps to full your gauge is OK. Do not hold the jumper to ground as it can cause damage.

On my Baha my gauge wasn't working either, and all I did was run a new ground wire from the sender to neg. on battery, and presto gauge works fine now, somehow it must have lost ground from factory wiring?

The resistance numbers you've quotd are correct for US standard guages like Teleflex, Livorsi/Gaffrig, etc. VDO as came with Formula are reversed and different range as well.

Yes. It must have lost the original ground.
Probably was removed from the tank.
Now... granted, I have never owned a Baha.
But....
In a standard set up the tank is grounded and the sending unit gets it's ground from the tank. (through the housing)

Your tank is now grounded through your sender (via the battery), rather than the opposite.