Fuel level indicator has been reading at or near empty since I bought the boat. Prev owner said he had replaced the sender but it didn't fix the gauge readings.

Received and installed my Hardin Marine solid state fuel sender today. Made my tank depth measurement and cut it so it clears the bottom by 1 inch.
Hooked up the 2 wires and tried to calibrate the "Empty" capacitance with sender out of tank.

Instructions say to apply power and gauge needle should cycle from E to F a few times and stop on E.
Gauge would only go up to abt 1/4 and then drop to well below E (only made 1 cycle).

Discovered I have one of the few 0-90 ohm SW gauges made. Hardin sender is only compatible with 33-240 ohm gauges.

Bought and installed a Gaffrig 33-240 ohm gauge.

Tried the "Empty" cal again and needle only climbs to just below 1/2 tank then drops to just above E (only made 1 cycle again).
Shut off ign and placed probe in container full of gas. Ign back on, and needle only goes to just below 1/2 tank.

Sender is an "Auto Cal" version and has no adjustment screws.

Re-connected the original float type sender and I get good readings at empty and full, but in between, sender is intermittent. I does seem to prove the gauge and wiring are OK however.

Tried calling Hardin but they were already gone for the holiday weekend.

Spoke to rep at CP Performance, but he had no clue.

Anyone run into this problem before?

Yup......with Gaffrig gauge and sender. Never did get the new style sender to work. Sent it back to Gaffrig a couple of times and they had me do the calibration deal a bunch of times. It would work on a trip for a while then we would stop somewhere and when we start up to go again it would not work. I could not depend on it. I put the old float type back in and it works fine. Wasted my money on what I thought was the latest stuff and would be better.