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Was out this weekend and finally filled the gas tank. Gauge still reads half tank. Tapped it a few times with finger and dropped to quarter tank and stuck there entire day. I know there's supposed to be a float in the gas tank. Is there something else that I should check prior to pulling the floor up and digging into the gas tank?

If tapping on the gage made it shift from 1/2 to 1/4, then it sounds like your problem is either the gage, or the wiring at the gage (loose connections).

Also, you can test the sending unit without accessing the tank in the floor. You just need a digital electrical meter for ohm readings:
. Disconnect the "S" lead from the back of the gage.
. Check the resistance ("Ohm" reading) of the sending unit...check between the "S" wire and ground.
. According to Faria, the Ohms should be:
--- 240ohm at Empty
--- 203ohm at Half Tank
--- 33.5ohm at Full
When you rock the boat, you should also see a fluctuation in the ohms because of the sloshing.

If the sending unit seems to check OK, and the gage reads wrong even with cleaned up wires, then replace the gage.

http://faria-instruments.com/site_manuals/IS0085E.pdf

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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings