Fuel gauge showing 1/2 full but actually nearly empty

[richierich]

Dear jeanneau owners
Recently had a near death experience when leaving mykonos 2 NM out engine stopped showing just under 1/2 full on tank. Drifting with just 3 knots close to delos rocks !! After opening 2nd tank the full 200 l flowed in.. has any one had This problem?

[tilo]

I always keep an eye on my fuel gauge, but I never trust it. It's the engine hours that drive me to the fueling station. It's a very conservative approach, but it keeps me out of trouble.

[shenandoah]

Richierich,
We have had several issues with the guage just sticking at a certain level. Sailed to the Bahamas and back this winter with a guage that read empty the whole time. 

We replaced the censors in the tank and it seems to work now, but I only use it as a rough guide. It is important to know the approximate fuel consumption per hour and keep track of the hours, and don't wait too long to top off. There is no such thing as too much fuel. 


Warm regards, 

Chuck

[Mistroma]

Yes, gauge sticking seems to be common. I calibrated mine and encoded it into my replacement display. The ESP32 based system was usually withing 5-10 litres but sometimes stuck after filling. I'll probably swap the sensor to one using a load of reed switches as that should be more reliable.

I also log engine hours at that's always been fairly reliable as consumption for my 4JH4AE is always around 2.2 - 2.5 litres per hour. I never place complete trust in the gauge.

[Charlie-Bravo]

My gauge generally over estimates the fuel quantity, and then drops rather quickly , which told me not to rely wholly on gauges.
I use a well known ‘average’ for diesel engines is … horse power = litre’s an hour , and it seems to work , with error on the right side of caution , my 30hp engine actually seems to return 2.6 L / hour with average use over a 3 week cruise, and I use this as the basis for consumption, I always take at least 60L in cans as many routes have no reliable supplies, and double check my usage en route by seeing how much I can get into the tank.
As said before, you can’t have too much fuel ……… even though we are sail boats !!! Logging engine hours and adding them up now and again prevents disaster .

CB

[sitara]

My gauge has been showing full for the last few months, i track engine usage with the hour meter and estimate fuel usage. Just as well i fixed the hour meter.

[Camira]

My gauge always shows full for quite some hours before then dropping quite quickly, like many others it would seem I log engine hours and on every fill up I check the hours I get from the tank which gives me all I need to know.

[rene460]

Hi Richierich,

On the SO30i, the tank is definitely not rectangular as it fits into a portion of the hull which slopes fore and aft as well as side to side.  I am also suspicious that the float hits the top of the quite small tank, (only 50 litres), with the top section of the tank, which has the largest area, not yet filled.  The gauge stayed on full for the longest time then fell quickly as others have described.

I made a practice of recording the fuel gauge needle position and the quantity to fill each time I filled up.  It was indeed only half full when the needle showed the first sign of dropping from the stop on the full side.  I used a combination of engine hours until the needle came into range, then used my logged data to remind me what was left.

But you mentioned an anomaly with your second tank.  I am not sure quite what symptoms you are describing.  Certainly I would expect that only one tank should be open at a time to prevent air being sucked in from the nearer empty tank.  Also once down near a quarter, there could be a fair amount of sloshing of the tank level which may also lead to air pickup, especially if motor sailing.  Some issues will relate to which tank is low and on which tack you are motor sailing.  Does any of this address your specific problem?

rene460

[richierich]

Hi thanks for your responses. its all been fixed by the yard at $$$ but lets hope its not a recurring one 

[NZL50505]

Just to set your expectations, even when these guages are ‘working’ properly they are still notoriously inaccurate and ususlly report more fuel (or water) than you really have.

So despite a yard ‘fix’ treat with great caution and use engine hours as your primary indicator.

The only way to fix is to replace with a properly calibrated system eg a BEP sensor & monitor (which is what I put into my previous boat). It was accurate to within 2-2 litres.