Fuel gauge self calibration?

[X5oh]

I have just resurrected my 2003 Palm Beach 175 CC from a long sleep. The on board fuel tank was drained and fuel lines were secured for the last 5 years. I have just purged the tank again and purged accumulated moisture with a hand pump the best I could. I've added a clear sump filter/water separator in line and was able to visibly see and remove additional water until I had a clear indication. I originally added 6 gallons of fuel to the tank for starters to test run and also gauge checks. Engine run was fine but the gauge read slightly below "0". I then checked all grounds and cleaned and reattached gauge, still below "0" but it does flinch when the ignition is turned ON. Next I removed the sending (Wema) 6" and slid the float up and down, the gauge responds accordingly. Reinstalled the gauge and added 8 more gallons of gas, switch ON, still reads Empty. Again I removed the sending unit and filled a jar with fuel and submersed the unit to verify the float travel, good indications. Reinstalled then changed dashboard indicator, still empty indication. I then called the original dealer and he thought the 175cc came with a 30 gallon tank so I added another 6 gallon. Sure enough the gauge came up to just under 1/4 tank which made me confident that the system is working but a little heavy on the Reserve fuel indications. Now back to my original hope and question; Is there a Gauge on the market that can be self adjusted in order to tailor the indications to fit my requirements? My gauge is a standard American resistance 240-30 OHM Gauge

 

[Bt Doctur]

the sender is adjusted for the depth of the tank

 

[UncleWillie]

If the sender is in the Front of the tank and the boat floats bow up a little, you can expect the gauge to be very pessimistic.
My sender is in the rear of the tank and is very optimistic. It reads full for the first 3/4 of the tank and then quickly swings toward empty.
When you removed the sender was the fuel in the tank nearly up to the top? The float needs fuel in order to float.
If you are on a trailer make sure the boat is level.

Boat fuel gauges are famous for being nearly useless.
Yours will be good to confirm that you filled the tank before launching, but that is about it.
Full means Full, anything else is just a guess.

If you want to know how much fuel you have with any accuracy, you will need to install a Fuel Management System that measures the fuel flow through the fuel line to the engine and computes the fuel remaining in the tank.

 

[X5oh]

My sending unit is mounted in the rear of the tank, I had put about 14-16 gallons in it and it was level on the trailer. Put another 5 gallons in and it read slightly over a 1/4. Definitely going to check on a Fuel Management system. If affordable that might have to be my plan, if not I'll just carry a few gallons in a small portable unit with a quick connect.

 

[UncleWillie]

Fuel management systems are not cheap. At least not by my standards.
Faria used to market a unit in the $200 range but it does not seem to be available any longer.

Your 6 inch Wema Sender may be too short for your tank. They are available in 0.5 inch increments.
Unless the tank is less than 6.5 inches deep you are only measuring the upper 6 inches.
I would think that a 30 gallon tank would be deeper than 6 inches.