What is this “LF” cap/knob?

[Bill Seal]

Nope, magnetic float and reed switches. Old School. Works with standard automotive gauge.

[Jim Cate]

and since I only use about 1- 1.5 gallons per day sail, there's no way I could keep track.

Bill, I don't understand this! If you have an engine hour meter (and you should), and you know your average burn rate, it is easy to keep track of consumption. The length of your daily usage doesn't enter into the calculation at all... just the total hours since filling up.

I'm pleasantly surprised to hear that your (and Pilot's) fuel gages are accurate. All the one's I've ever had were moody to say the least, and pretty damn inaccurate as well.
Much of the difficulty lies in the peculiar shapes that boat tanks often have. Calibration can be tricky!

I reckon that if they've mastered the fuel gage, the cure for the common cold will soon be in hand as well!

Jim

[georgeg305]

There is another reason for the access port. In my area, N. Florida ) with temp changes and humid air, one can build up water in the tank ( condensation, water in fuel, etc. ) With water in the tank, in our climate, algae or more properly, bacteria, can grow in the tank. ( they live in the water and eat fuel ) That is why the fuel intake line is usually up off the bottom of the tank. You may want to open the tank and suck the gunk off the bottom periodically.

[lvictorlucas]

Just for your information the "LF" on the plug signifies the material is Lead Free.

[jamhass]

If you are willing to spend a few more bucks, try the TankTender. No moving parts (at least not in the tank) and they are dead accurate. You can use the same unit for multiple tanks, both water and diesel. No need to open the tank to make a measurement, no electrical parts to corrode. Very simple installation. Can even get a kit to use it for a holding tank.

[desodave]

"If you have an engine hour meter (and you should), and you know your average burn rate, it is easy to keep track of consumption. The length of your daily usage doesn't enter into the calculation at all... just the total hours since filling up."

I agree completely with Jim. I'm a coastal cruiser and haven't used my fuel gage for years. I keep a log of fill-ups (inc date, quantity of diesel, & engine hours) and regularly calculate average consumption. In my case, that means that I've used half a tank if I've run 25 hours since the last fill-up.

[NPCampbell]

Originally Posted by Ecos

I think it might be called a "capacitive fuel quantity " probe.

Another name that my automotive unit went by was "floatless fuel sending unit". They come in varying lengths and I calibrated mine to drive a standard 0-90 ohm fuel gauge.