Lund gauge or sending unit?

[law57]

The gas gauge of my Lund Alaskan doesn't work correctly. It says 'empty' when the tank is about 1/2 full. I'm wondering 1) is this the gauge or the sending unit - how would I tell? 2) is this problem common to Lund and/or boats in general? This is the first boat I've owned with an internal gas tank.

I know - I know... I can just ignore it since I know it is happening. But then it won't happen and I'll actually be empty. Or I can carry a 2 gallon can of gas with me - a pain in the butt.

I suppose I could take the time to replace the gauge first and then the sending unit if that (gauge) doesn't work. But if this is a common problem, I gain little or nothing.

Any ideas?

[Pooch]

Boat fuel tank gauges seem to be notoriously inaccurate. Probably because of how the boat is setting in the water or on the trailer. If the fuel tank was setting perfectly level and not moving side to side or front to rear then the gauge could be pretty close.

My last boat had a twelve gallon "portable" tank and I could actually check fuel level with a dowel rod I carried. I trust the dowel rod far more than the electric gauge in my new boat.

One would think that with the advanced electronic chips in today's boats that there would be two sending units (one in front and one in the back) mounted in the fuel tank. A small circuit could average and extrapolate the two readings and give us better and more trustworthy fuel levels readings.

Pooch

[REW]

Law,
To test the gauge, you can remove the wire from the sending unit to the gauge and replace the sending unit with a variable resistor. i.e. similar to a volume control on a radio.

Connect one side of the resistor to ground and then attach the gauge wire to the middle wire of the variable resistor. Then, with the power turned on to the motor, which turns on voltage to the gauges, you can turn the dial on the variable resistor and the gauge should move up and down from empty to full.

If you have a 150-200 ohm variable resistor you can use it to test the gauge.

If you have an ohm meter, you can use the ohmmeter to check the sending unit.

Remove the sending unit from the tank. Clip one lead on the edge of the sending unit or ground. Clip the other lead to the center screw on the sending unit and then with the ohmmeter set on RX1 move the arm up and down. In the down position, the resistance should be about 240 ohm for a Teleflex gauge,and about 33 ohms with the arm in the full up position of the unit.

If these readings are correct, the sending unit is all right.

If, when you connect the sending unit to the gauge with the sending unit grounded and then move the lever from the top to the bottom and you do not get the correct reading on the gauge, the gauge itself is likely defective.

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https://www.jamestowndistributors.co...t.do?docId=833

A white paper on testing the sending unit and gauge on a boat.

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Here are a few different You Tube videos that go through the various steps to check both the sending unit, as well as the fuel gauge itself on a boat when the fuel gauge does not work correctly:

https://www.youtube.com/results?sear...auge+on+a+boat

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But to put it in very simple terms.
A fuel gauge is nothing more than a small ammeter. When the meter measures a low flow of current the gauge sits at empty. When the meter measures a larger flow of current, the gauge sits at full.

The sending unit is nothing more than a variable resistor that changes value as the dial is turned so to speak as a result of the sending unit arm going up and down.

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Best wishes.

[law57]

Originally Posted by REW

Law,
To test the gauge, you can remove the wire from the sending unit to the gauge and replace the sending unit with a variable resistor. i.e. similar to a volume control on a radio.

Connect one side of the resistor to ground and then attach the gauge wire to the middle wire of the variable resistor. Then, with the power turned on to the motor, which turns on voltage to the gauges, you can turn the dial on the variable resistor and the gauge should move up and down from empty to full.

If you have a 150-200 ohm variable resistor you can use it to test the gauge.

If you have an ohm meter, you can use the ohmmeter to check the sending unit.

Remove the sending unit from the tank. Clip one lead on the edge of the sending unit or ground. Clip the other lead to the center screw on the sending unit and then with the ohmmeter set on RX1 move the arm up and down. In the down position, the resistance should be about 240 ohm for a Teleflex gauge,and about 33 ohms with the arm in the full up position of the unit.

If these readings are correct, the sending unit is all right.

If, when you connect the sending unit to the gauge with the sending unit grounded and then move the lever from the top to the bottom and you do not get the correct reading on the gauge, the gauge itself is likely defective.

------------------
https://www.jamestowndistributors.co...t.do?docId=833

A white paper on testing the sending unit and gauge on a boat.

---------------
Here are a few different You Tube videos that go through the various steps to check both the sending unit, as well as the fuel gauge itself on a boat when the fuel gauge does not work correctly:

https://www.youtube.com/results?sear...auge+on+a+boat

======================================
But to put it in very simple terms.
A fuel gauge is nothing more than a small ammeter. When the meter measures a low flow of current the gauge sits at empty. When the meter measures a larger flow of current, the gauge sits at full.

The sending unit is nothing more than a variable resistor that changes value as the dial is turned so to speak as a result of the sending unit arm going up and down.

----------------------
Best wishes.

Thanks Pooch and REW. I could go thru all that trouble or just pull the pin on a new Alumacraft 180 Summit!

[T Mac]

This is a common issue on boat fuel tanks...
Only a couple companies make almost all of them.
Usually it is in the sending assy.


What year is the boat?

[law57]

Originally Posted by T Mac

This is a common issue on boat fuel tanks...
Only a couple companies make almost all of them.
Usually it is in the sending assy.


What year is the boat?

The boat is from 2012. I don't have a ton of hours on it. Nice rig. But I would like the fuel gauge to work accurately - if possible.

[REW]

Law,
Now, lets not give up.

A fuel gauge and sending unit is very simple.

To be sure, just order a new fuel gauge, and the correct sending unit for your fuel tank, install them both and you will have a working fuel gauge assuming that there are no broken electrical wires in the boat.

Remember, the sending unit sends fuel information on the height of the measured level.
So, the sending unit needs to be calibrated for an empty tank and a full tank, or be selected to correctly measure fuel in a tank having the same height as the tank in your boat.

You can buy the pair of units for under $100 and probably much less.

I don't believe that you can buy a different boat for $100.

Also, by having a working fuel gauge on your current unit and you decide to sell it; a defective fuel gauge will subtract more than $100 from the price that you get when you sell the boat.

Good luck.

[GOS]

2017 Lund Pro Guide: The gas gauge is unreliable, as in WTH off. Lund factory OK'd changing out the sending unit under warranty back in the fall of 2016. It made virtually no difference.
Here's what I found out in the process: When ethanol fuels came on the scene, the float arm on the old style sending units started to rust out. The industries answer to that is a sending unit that is essentially a round tube that has a float around the outside. Problem is the round tube, and hence the float, most likely does not reach down to the bottom of the fuel tank. Therefore the float reads empty when there may still be XX gallons left in the tank.
I gave up on the issue of the gauge being anywhere near accurate. I have a Merc. They ran a special on their Vessel View Mobile accessory this past spring for $150, which is a big chunk off full retail. I keep track of fuel consumption via the VVM. How accurate is it? I filled the tank this spring and have not added any fuel yet, so I really don't know for sure, but I think the consumption it's showing is pretty darn close and way better than that POS gauge/sending unit set up. I installed the VVM myself.
Hope this might help, Gregory

[REW]

GOS,
I expect that your comments are correct.

However, there are millions of cars on the road that use fuel ranging from "corn fed - $100% alcohol to high test non leaded pure gasoline.

Virtually all of these vehicles have fuel tanks with sending units in the tank and gauges that are in place to be viewed by the operator of the vehicle.

Many of these vehicles are many many many years old and the gas gauge is still 100% accurate.

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So, just because one particular boat manufacturer uses a fuel gauge that is not accurate and not long lasting does not mean that there are not accurate and long lasting sending units and gauges on the market.

Do your research, find the unit/s that will do the job. Remove the current sending unit, and gauge and replace with the sending unit and gauge of your choice and move on.

There are plenty of marine craft on the fresh water and salt waters of the world that are 20-50 years old that have accurate fuel measuring systems and are in use every day.

Be safe

[lawson2343]

Originally Posted by law57

Thanks Pooch and REW. I could go thru all that trouble or just pull the pin on a new Alumacraft 180 Summit!

Law57, buying a new Alumacraft won't guarantee you a better gas gauge!

I have a 2016 Trophy 175. My buddy has a 2017 Edge 185. Both of us have learned the hard way that the gas gauge is off. We have both run out of gas when the gauge is just under a 1/4 tank! I was prepared and had a 5 gallon backup. He was not!

I talked to the dealer about a defect and he said likely not. He said the gas gauges are notoriously off. I just live with it.