Fuel Gauge

Bygracealone · #1 05-28-2011, 09:51 AM

Hey guys,

There is a discrepancy between the reading on my fuel gauge and the reading on the manual gauge on the tank. For instance, the remote gauge is reading 1/4 full while the gauge on the tank is reading close to 1/2 full. I'm not certain about the capacity of the tank; it's not stock. It's either 80 or 100. From my best estimations, there should be approximately 40 gallons of fuel in the tank right now, so I'm thinking it's likely an 80 gallon tank and that the reading on the tank gauge is correct. Any ideas as to what might be causing the discrepancy? Are there different gauges designed for specific capacities of tanks? I didn't think so, but thought I'd ask.

Thanks in advance for your help.

tsubaki · #2 05-28-2011, 10:23 AM

Yes but they are governed by the length of the probe.
A major problem is determining just where you want the readings to be accurate.
A square or rectangle tank is pretty easy to get correct and calibrate the sending unit, the volume varies proportionally with the level of the fuel.
A belly tank on the other hand gives the impression the lower the fuel level is the more quickly it runs out of fuel but seems to not consume as much when fully loaded.

Or am I not reading your questions correctly?

tsubaki · #3 05-28-2011, 10:30 AM

If the sending unit came with the tank, there is a good chance they calibrated it at the half way mark.
And is the fuel tank sitting level when you are taking the readings?

Bygracealone · #4 05-28-2011, 10:37 AM

Thanks for the response T,

I might not have been as clear as I could have been. I would like to have the remote gauge on the console to reflect the reading on the gauge that's on the tank.

The gauge I installed on the console doesn't have any options for calibration. So, do I simply need to buy another gauge (that would be a bummer because I just replaced all the gauges and they all match currently...) or is there something else causing the discrepancy?

It seems like the remote gauge is acting as though I have a 120 gallon tank (which is not totally outside the realm of possibility).

Curapa · #5 05-28-2011, 01:07 PM

So you have two gauges and one sending unit? I know I have see 30 ohm and 33 ohm gauges. Could that make a differnce?

tsubaki · #6 05-28-2011, 01:15 PM

Normally it is only possible to make adjustments on the sending unit and not the gauge.
Depending on the type of sending unit you have, you can do the adjustments that you are describing.
If the sending unit is the stem type, usually the only adjustments possible would be for the tank depth.
The usual sending units of the arm type can be manipulated some in order to reflect a know level (as in your case) by bending the arm at some point between the float and the sender itself.
Bending the arm to make the float deeper would adjust the sender toward a more "full tank".
In your situation, it is probable in doing this, the arm may contact the top of the tank when not quite full of fuel.
If it were me, I'd have to find the actual tank size, even go to the point of draining it, refilling it to full, then remove 1/2 of the fuel and then do the adjustments to the sender or the manual portion, whichever is incorrect.
Again, this is making sure the tank is level.

Bygracealone · #7 05-28-2011, 02:11 PM

Quote:

Originally Posted by Curapa

So you have two gauges and one sending unit? I know I have see 30 ohm and 33 ohm gauges. Could that make a differnce?

Curapa, I guess the gauge I'm referring to at the tank is actually part of the sending unit; it's registering one reading while the gauge at the console is registering a different reading.

Bygracealone · #8 05-28-2011, 02:13 PM

Quote:

Originally Posted by tsubaki

Normally it is only possible to make adjustments on the sending unit and not the gauge.
Depending on the type of sending unit you have, you can do the adjustments that you are describing.
If the sending unit is the stem type, usually the only adjustments possible would be for the tank depth.
The usual sending units of the arm type can be manipulated some in order to reflect a know level (as in your case) by bending the arm at some point between the float and the sender itself.
Bending the arm to make the float deeper would adjust the sender toward a more "full tank".
In your situation, it is probable in doing this, the arm may contact the top of the tank when not quite full of fuel.
If it were me, I'd have to find the actual tank size, even go to the point of draining it, refilling it to full, then remove 1/2 of the fuel and then do the adjustments to the sender or the manual portion, whichever is incorrect.
Again, this is making sure the tank is level.

Thanks T. I'm going to try to contact the previous owner and see if he can recall what size tank he put in it. I'll let you guys know what I find.

Your help is much appreciated.

macojoe · #9 05-29-2011, 05:48 PM

i have a 110 gal tank i use 25 gal most trips and fill after every trip, so i no give a crap about the gauge!!
this boat the Sea Ox longest trip was 80 miles round trip, and used just 30 gal

Bygracealone · #10 05-29-2011, 06:25 PM

Quote:

Originally Posted by macojoe

i have a 110 gal tank i use 25 gal most trips and fill after every trip, so i no give a crap about the gauge!!
this boat the Sea Ox longest trip was 80 miles round trip, and used just 30 gal

I might follow your lead there MJ!