What is this “LF” cap/knob?

[SailAwy]

Hey all, tinkering around and trying to figure out some maintenance on my engine. Came across this when I opened the panel to my fuel tank. Anyone know what this cap is for? I don’t have a fuel gauge, and was hoping to be able to install one rather than just guess when I’m about empty. Would this be a potential fitting to install one?

Any help is surely appreciated!

Thanks!

[Me-and-Boo]

That is the big hole to drain and clean the tank.

[Stu Jackson]

Originally Posted by SailAwy

>>>>>>>>>>>>>
I don’t have a fuel gauge, and was hoping to be able to install one rather than just guess when I’m about empty.

>>>>>>>>>>>>>>>>>>>

Why bother? Just keep track of your fuel consumption. Many of us have found it to be more accurate than fuel gauges.

[SailAwy]

Originally Posted by Me-and-Boo

That is the big hole to drain and clean the tank.

Was hoping that was the case. No issue with uncapping, right? Meaning, l don’t have to worry about pressure, priming, bleeding every time I unscrew? Can you tell I’m learning as I go? Haha.

Thanks!

[SailAwy]

Originally Posted by Stu Jackson

Why bother? Just keep track of your fuel consumption. Many of us have found it to be more accurate than fuel gauges.

Certainly a simpler option. Will try that for a season and see how good my estimates are.

Thanks!

[Jim Cate]

If the pic is of the top of the tank, you could make a calibrated dip stick to measure the level... that's what we did. run the tank dry, pull the plug for access, fill (in our case) in 20 liter increments and check and mark the level on the stick at each increment.

This is quite accurate, inexpensive and will help you with establishing your fuel burn rate.

Jim

[DougR]

Nice clean installation.......

Top to bottom the hoses are:
- green static electricity ground wire from tank to deck fill plate
- tank breather hose
- tank fill hose
- fuel return hose from engine
- fuel feed hose to filter and engine with shutoff valve

Jim Cates idea of a dip stick is good. If it were me I would remove the large LF cast iron plug and drill and tap a 3/8 threaded hole in the center of it and use that smaller hole for a dip stick access hole. Use a brass 3/8 " plug. That way less hassle sealing the threads every time you check fuel level.

If the cover for the tank is a screw down wooden cover you might find it convenient to install a plastic 5" inspection port into the cover for easy access. If not screw down, don't worry about it.

No problem with pressure or bleeding if you open the port...just don't fill the tank with the port open!

DougR

[SailAwy]

Originally Posted by Jim Cate

If the pic is of the top of the tank, you could make a calibrated dip stick to measure the level... that's what we did. run the tank dry, pull the plug for access, fill (in our case) in 20 liter increments and check and mark the level on the stick at each increment.

This is quite accurate, inexpensive and will help you with establishing your fuel burn rate.

Jim

Thanks Jim. It is the top of the tank. I’ll give this a go. Great suggestion.

[SailAwy]

Originally Posted by DougR

Nice clean installation.......

Top to bottom the hoses are:
- green static electricity ground wire from tank to deck fill plate
- tank breather hose
- tank fill hose
- fuel return hose from engine
- fuel feed hose to filter and engine with shutoff valve

Jim Cates idea of a dip stick is good. If it were me I would remove the large LF cast iron plug and drill and tap a 3/8 threaded hole in the center of it and use that smaller hole for a dip stick access hole. Use a brass 3/8 " plug. That way less hassle sealing the threads every time you check fuel level.

If the cover for the tank is a screw down wooden cover you might find it convenient to install a plastic 5" inspection port into the cover for easy access. If not screw down, don't worry about it.

No problem with pressure or bleeding if you open the port...just don't fill the tank with the port open!

DougR

Thanks for the hose ID Doug!

It is a screw down cover but I have one section over the inlets that is just a lift off cover. I’ll look into refitting a dipstick hole. For the time being, when I reseal the plug after each time I unscrew, would I use an actual sealant or fuel resistant Teflon tape?

[HopCar]

If you want an electric gauge, I bet WEMA makes a fuel level sender that will screw right in where that plug is. Liquid Sensors - Marine Diesel, Fuel, or Water Level Sensor

[HopCar]

If you decide to go with the dip stick idea, get some water finding paste. Smear a little on the stick and you’ll be able to tell if there is water in the tank. The paste turns bright red when it touches water.

[Bill Seal]

If there's a straight shot to the bottom of the tank, (and it's 1.5" NPS) you can get a WEMA gauge sender that just screws in.
I know the haters are going to chime in, but mine works perfectly, and since I only use about 1- 1.5 gallons per day sail, there's no way I could keep track.
oops, I see HopCar beat me to it.

[SailAwy]

You all are great! Thanks!

[a64pilot]

Originally Posted by Bill Seal

If there's a straight shot to the bottom of the tank, (and it's 1.5" NPS) you can get a WEMA gauge sender that just screws in.
I know the haters are going to chime in, but mine works perfectly, and since I only use about 1- 1.5 gallons per day sail, there's no way I could keep track.
oops, I see HopCar beat me to it.

My fuel gauge at 32 yrs old is astonishingly accurate as well. I did have to replace the sender though, original was a float on an arm, the new one is made by WEMA and is a float on a tube, old one moved a contact across wire windings and read resistance, new one works by magic I suppose.
My theory is that my fuel tank is almost square or at least has significant depth, and that leads to an extremely accurate gauge.

[model 10]

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