My used boat has a 25 Gal. built in fuel tank. The gage comes alive when the ignition key is turned on and rests at just slightly above half-tank when the tank is full to the neck. After I run out about 8 Gal., the gage reads just below half tank. In short, it's not doing me much good as an indicator. Is there a test to determine where the problem lies (gage or sender)? Can either of these be repaired or calibrated?
