fuel gauge

[Rick.johnson]

Hi Guys
i have a 1987 hunter legend 40 with a yanmar 4jh-e engine
an the fuel gauge is mounted on the wood panel in the aft berth

Do i need to have the ignition key on to have the gauge properly work
when i tap on tank is sounds to be about 1/4 full but with the key off press button on fuel gauge
it light up an swing to full
what is the proper way to measure fuel level ????

thanks guys

 

[JoeWhite]

Yes, ignition must be on

 

[Rick.johnson]

Ok Thanks Joe I will be testing it this weekend
Rick

 

[Ralph Johnstone]

The "ignition key" normally disconnects all electrical power from the engine so your level should show "0" at this time. With what a previous owner may have done, all bets are off.

 

[Rick.johnson]

Will be testing it this weekend
Thanks Rick

 

[capta]

I'd think it odd that the light works when the key is off, so perhaps the gauge does too.

 

[Ralph Johnstone]

Will be testing it this weekend
Thanks Rick

Please follow up. The results would be interesting.

 

[flightlead404]

Will be testing it this weekend
Thanks Rick

Either way I wouldn't trust it. Having flown thousands of hours in aircraft with similar fuel gauges and sensors (resistive float), and similar issues regarding things like degrading contacts, heeling/banking/pitch effecting the reading and generally low resolution, you're much better off using time.

Use the hour meter on your engine and always fill up to the same point (for me, when it starts to foam out the filler) you'll figure out pretty quickly what your burn rate is. I know I burn 0.72gph @ 2,600 rpm doing 6.5kts in flat water. Much better for float planning etc than any lousy fuel gauge.

 

[Ralph Johnstone]

Will be testing it this weekend

Go high tech and use a stick. No, I'm quite serious.

I have a small port in the top of the fuel tank for sampling fuel and also use it to check the calibration of the fuel gauge. Dip the tank with a 1/8" wooden dowel. So far haven't had any problems with a 24 year old WEMA float gauge.

 

[JamesG161]

So far haven't had any problems with a 24 year old WEMA float gauge.

Since I have my fuel tank shop drawing, I calibrated my tank ±5 gallons. Saba = boat name.

The Green Bar = Wema float length.

The Colors are shown on my Wema Gauge

Jim...

 

[Ralph Johnstone]

The Colors are shown on my Wema Gauge

Sounds exotic. I only have the 0 - 1/2 - 3/4 - FULL on my black & white WEMA welfare brand gauge :

Can you post a picture of this colour coded gauge ?

 

[JamesG161]

Can you post a picture of this colour coded gauge ?

I switch to F3 and then the gauge stabilizes.

I keep my gauge calibration verified, each time I fill the tank.

On another Tank graph, I keep aboard, I mark the level on that fill.

Rich Stiger asked me why noted the emergency level.

Note how I shaded the Red Area.

Jim...

 

[Ralph Johnstone]

I keep my gauge calibration verified, each time I fill the tank.

I've missed something here. Is calibration by the volume dispensed on the vendor's fuel meter or is there some other method ?

 

[JamesG161]

Is calibration by the volume dispensed on the vendor's fuel meter

Yes, but just the first time I had a near empty tank
_____
My pictogram is to scale, by the shop drawings.

The panel gauge looks to be linear on the dial. The tank volume is NOT linear by its shape.

Note the Blue area on diagram = Blue area on the Gauge
_____
By the help of the fuel attendant, he would add a gallon, I would note the change on Blue Dial pointer.

Thus I noted 5-8 gallons in that calibrated Blue Area.
_____
I used a spreadsheet to calibrate it.

The last time I filled my tank, I told the fuel guy, give me 15 gallons and hold.

Then by my calibration curve , I estimated 18 total , and I actually did 18.5 gallons.

Jim...

 

[Dalliance]

I think the answer may be “it depends”. It no doubt varies by boat and whatever mods a previous owner might have made too. My ‘82 H30 has a fuel gauge next to the electrical panel that is powered on the same circuit as my speed and depth instruments. This kind of makes sense to me as the engine ignition should be off when you‘re fueling. I don’t know if Hunter or the PO set it up that way. You mention a button next to your gauge, which sounds like an independent convenience switch of some sort. IDK.
I actually go by when I see foam backing up in the fill hose since I can’t see the fuel gauge from the cockpit while fueling and I’m not sure how much I trust it anyway, so it sort of doesn’t matter. I have a good idea how many gallons I need and have someone stand at the pump to call out 2 gal, 3 gal 4…. as I am fueling so I know when it’s getting close.