Inaccurate Gas Guage readings

[belsitj]

Hello
The gas gauge on my boat is not accurate. Is it the Gas Sending Unit that needs to be replaced? If so, is it difficult to replace? If anyone can give me some tips on how to do that I would appreciate it. Do I need to drain the gas to do it? Thanks in advance.

Joe

[Submarine Tom]

They're all in accurate. You're far better off to dip your tank, then you know how much fuel you have.

-Tom

[gonzo]

It can also be the gauge

[michael pierzga]

Originally Posted by belsitj

Hello
The gas gauge on my boat is not accurate. Is it the Gas Sending Unit that needs to be replaced? If so, is it difficult to replace? If anyone can give me some tips on how to do that I would appreciate it. Do I need to drain the gas to do it? Thanks in advance.

Joe

No its not difficult to replace. The sending unit will be installed thru the top of the tank. 4 or 6 screws and its off. Replacements are readily available at most marine store, engine shops.

If your tank is built over with a cabin sole or furniture and you cant access the tank top, then its a problem. You will have to hole saw or otherwise cut an inspection access hatch over the top of the unit


With a diesel tank there would be no need to drain the tank. With gasoline do be careful that you dont blow yourself up and burn down the whole marina when installing the sending unit

[CDK]

Specify "not accurate".
Does it show half with a full tank, 1/4 with an empty tank or does the needle keep moving?

[belsitj]

Thanks everyone for the feedback. The gas tank is easily accessible, not a problem there. The gauge needle does move but it seems like there is less gas in the tank than shows on the needle (I am paranoid about running out of gas on Lake Erie). Using a dip stick doesn't sound like an option because it is not a straight shot from the filler hole to the tank (my boat is an 18' Lund). I guess maybe the easiest way to see if it is accurate is to let it run out of gas and see where the gauge marks. Thanks everyone.

Joe

[michael pierzga]

Gas tank level sensors and gauges are always crude things and fuel tanks come in many different shapes.

If you install a new sensor remember to calibrate it. Add 10 liters of fuel...mark the gauge...add 10 more, mark the gauge.....

[belsitj]

ok, thanks for your advice on the calibration.

[CDK]

Originally Posted by belsitj

The gauge needle does move but it seems like there is less gas in the tank than shows on the needle (I am paranoid about running out of gas on Lake Erie).

OK, so the sender does work the way it should, no need to replace it.
The problem is in the voltage regulator belonging to the gauge. It may be internal, but most boat builders use an external one. It is a small square metal device, mounted with a lug at the back of the dash. It has one wire coming from the key switch B+ and one going to the gauge, the lug is supposed to be connected to a ground wire. If the ground contact is corroded or the regulator has died, the output voltage is too high, causing the gauge to show gas that isn't there. It is a cheap part, replaceable in a few minutes.

If there is none, you have bad luck: the regulator is internal and you have to exchange the gauge.