Beneteau Oceanis 40 fuel gauge is inaccurate

[Cadence]

Originally Posted by AFKASAP

I am sure that you would assume it to be inaccurate, but I can confirm that it really is (at least on my boat).

Ours is a 2008 2 cabin version, which is supposed to have 200L tank.

My tank showed a little under half full and when I filled up and I managed to put in 187L. So either the tank is bigger than rated or the gauge is very inaccurate.

Anyone have info on this?

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If your fill is a straight shot into the tank. A graduated stick is the real answer.

[Stu Jackson]

Originally Posted by AFKASAP

I believe there is nothing wrong with the sensor. It is just not calibrated to take into account that the tank gets narrower at the bottom.

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Of course, that's THE answer. The tank is not linear, the fuel sender is.

This is a recurring question. It's also the reason that folks don't trust their fuel gauges, they're not like cars.

As one poster stated: keeping track of engine hours and gallons put in will give you a better idea of where you are than the gauge will

Do this, make up a fuel consumption table or spreadsheet (like this: Fuel Log) and forget about the gauge.

Good luck.

[nigel1]

I was talking to Wema UK today, they can calibrate a gauge to allow for the tank shape, but it'll cost, I did not dare ask.

[cabo_sailor]

Originally Posted by sck5

an even better way to keep track if you have a straight line fuel fill pipe: get a wooden dowel that reaches to the bottom of the tank and make marks on it. Foolproof if your boat is set up so that it is possible.

That's what I did only my tank has a prefab dipstick. I have a fuel gage but once it shows a half tank I start checking with the dipstick and the Mark I eyeball.

Rich


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[trishark]

We own a 2009 Beneteau 40 which may also be called the Oceanis. Our 52 gallon tank has a step along the forward edge about 2" below the top of the tank. I have been told that the sender rod is installed straight which holds the float 3 to 4 inches below the top of a tank that is only 10" or so tall. Diesel level has to drop to around 2/3 full for the level on the gauge to start dropping. This is consistent with what we see. I had planned to pull the sender and bend an arch in the rod that would raise the float up an inch or two above the shelf. I figured this would take several hours which probably meant 8 plus with issues and did not get it done b4 we left cruising. I just monitor engine hours and run a spread sheet to determine average consumption.

[nigel1]

I've just fitted the reed switch type tank gauge, and then filled the tank. It is much more accurate than the float type it replaced.
The tank is 250 litre. With 50 liter's added, gauge indicated 1/4, 100 liter's gauge at 1/2, 200 liter's in the tank and gauge indicated full.

[Slamjunk]

I wouldn't replace it.

My sender gave my gauge a bouncy needle. I pulled it and took it apart, was coated in a black film. I used a meter and the resistance flew everywhere as I moved it through its range. I disassembled it, cleaned the metal components with my companionway step as sandpaper. After reassembly it moved nicely through a 200 some ohm range.

I agree with the comments advising you to record and log your gauge reading vs how much fuel you put in. You can make a gauge correction card much like your compass should have. No indicator is perfect.


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[Liam Wald]

I have never trusted fuel gauges on boats.
I always keep track of how many hours the engine has run between topping off the fuel.
My boat has always averaged 1/2 gallon per hour cruising at 2800 rpm. (Yanmar 3gm30F)
I always enter engine hours in the ships log (I trust hour meters) daily.