Fuel gauge accuracy

[fox islander]

Does anyone have a fuel gauge on their C30 that is even remotely accurate? When mine reads almost empty I can only put in around 12 gal before the gauge reads full. I dont put in any more fuel after full as it can back fuel up into the vent line.
Wondering if anyone as installed an aftermarket fuel gauge system.

Thanks

 

[anchorclanker]

Fuel gauges are notoriously inaccurate regardless of the manufacture. Sometimes greater accuracy can be found by removing the sending unit and bending and or straightening the float arm so it falls closer to the bottom, or rises closer to the top, but ultimately giving a greater range of movement. Some panel gauges can also be adjusted (compensated) to read the sender more accurately. But realize that voltage has an effect, so its never going to be 100% reliable no matter what you do. The best suggestion is to use a dip stick in the tank like were taught to do with airplanes, or install a sight tube in the tank allowing you to see the actual level. Second is to know the average hourly maximum fuel consumption and keep track of the time and always top off the tank.

 

[Anonymous 121765]

Fox,

When I re-powered, I put in the Admiral panel. I removed my tank top readout, however, 3 years later both electric floats burned out. I put back the old float and made sure I adjusted the swing arm & float to fit my tank just like AnchorClanker described.

My accuracy is pretty accurate, but I also did something else. I emptied the tank bone dry. I carry my own fuel to the boat, I have a gas station with a high filtered diesel. Looks just like water.

I filled the first 6 gallons. I then took fingernail red poiish (not mine of course), and marked it where the needle was. Three more fills while marking, and I now have the accuracy I need. Another advantage is now I look and know just how much I need to fill it without going over.

CR

 

[Bob S]

I figure 1/2 gal per hour and use the hour meter. The fuel gage is approximate. I usually add 8-10 gal when I'm at 1/4 tank on the gage. Do you use that much fuel in a season?

 

[Stu Jackson]

Forget the fuel gauge, it's completely misleading. http://c34.org/bbs/index.php/topic,3841.0.html

 

[anchorclanker]

This gauge is 100% accurate.

 

[Stu Jackson]

That's true. Only "issue" is that a majority of sailboat owners do not have that kind of access to their fuel tanks. Good idea, though.

 

[fox islander]

...thanks for the discussion...sounds like I'd better start watching the hour meter.

 

[Maine Sail]

Fuel gauges are notoriously inaccurate regardless of the manufacture. Sometimes greater accuracy can be found by removing the sending unit and bending and or straightening the float arm so it falls closer to the bottom, or rises closer to the top, but ultimately giving a greater range of movement. Some panel gauges can also be adjusted (compensated) to read the sender more accurately. But realize that voltage has an effect, so its never going to be 100% reliable no matter what you do. The best suggestion is to use a dip stick in the tank like were taught to do with airplanes, or install a sight tube in the tank allowing you to see the actual level. Second is to know the average hourly maximum fuel consumption and keep track of the time and always top off the tank.

The gauges read the resistance of the sender at 33 to 240 Ohms. The circuit to the sender is not powered with 12V... The gauges can be pretty accurate but may not be accurate to the relation of the boats tank. In a "square box" they are pretty accurate, if adequately sized for the tank, but many sailboat tanks are anything but a square box thus they are more of a "guide" on some boats than accurate.

 

[jimmcgee]

but I also did something else. I emptied the tank bone dry. I carry my own fuel to the boat, I have a gas station with a high filtered diesel. Looks just like water.

I filled the first 6 gallons. I then took fingernail red poiish (not mine of course), and marked it where the needle was. Three more fills while marking, and I now have the accuracy I need. Another advantage is now I look and know just how much I need to fill it without going over.

CR

I like this idea. It takes the tank shape out of the equation.

Hmm, interesting though that Capt Ron used nail polish not paint...

 

[jrowan]

This gauge is 100% accurate.

As Stu said, a sight gauge will not work on a Catalina 30, or most any sailboat, because you can only view the top of the tank, where the existing gauge is installed. Although I was thinking of cutting a sight hole in the wooden coverplate where the tank is located at the aft end bunk board. I only view my fuel gauge about once a month, because it is so friggin hard to access the gauge, since you have to remove everything placed on top of the tank to see it.

 

[leftbrainstuff]

If you can't calibrate your fuel sender then you can calibrate the guage by noting the guage reading as you fill the tank from empty with set amounts. Using an indelible marker on the guage is simple.

 

[melliott0352]

I use a 1/4 inch thick length of wood dowel that I marked with a black maker at full, 3/4, half and 1/4. unscrew the plug on top of the tank and stick it in. I check the level after every other cruise or so to see if I need to bring fuel next time. I dont cruise much more than an hour or two each outing, so havent gotten near empty. Would be nice to have a reliable gauge, but so would winning the lottery!

 

[DanM]

Also, one variable in measuring resistance of the guage changes quite a bit... voltage. Engine running, voltage maybe 14.4vdc or so versus a few days out on the hook and first thing in the morning voltage maybe 12.1vdc or so. That's a pretty wide range really. If you were going to try some calibration technique it might be easiest to do it with the engine running and the batteries charged so as to take the voltage variable out of the equation. That being said, I use my hour meter.

DanM.

 

[Maine Sail]

Also, one variable in measuring resistance of the guage changes quite a bit... voltage. Engine running, voltage maybe 14.4vdc or so versus a few days out on the hook and first thing in the morning voltage maybe 12.1vdc or so. That's a pretty wide range really. If you were going to try some calibration technique it might be easiest to do it with the engine running and the batteries charged so as to take the voltage variable out of the equation. That being said, I use my hour meter.

DanM.

The input voltage on the sending units & gauges does not really matter as they will operate just fine from about 11V to 15V +/-. They read resistance and any changes derived from voltage up/down would be so minute at the needle as to not even be discernible..

The sender is not powered only the gauge is to have back lighting and to "excite" the needle thimble which takes virtually no current. They will pretty much operate from 11 - 15+ v . If your bank is below 11V you have more pressing problems...

 

[DanM]

Hmm, interesting. Mine varies considerably with the engine running versus shut down, so I always blamed it on voltage differential. Wonder what the difference could be attributed to?