How many unusable litres of fuel are there in a 150 litre tank?

[Harveyhall]

I have read a number of the older posting about poor fuel gauges on the forum and wonder if any one can tell me how many litres of fuel is not able to be reached by the fuel pickup? 

I believe I ran out of fuel with the gauge showing 1/4 but when I was able to fill the fuel tank with about 117 litres. Before that I changed both fuel filters thinking that it may have been a fuel problem after we sailed to the dock.

Did anyone know approximately how much fuel is unusable on a 2005 36 Cruiser I believe with a 150 litre tank?
Thanks

[Lawry]

So are you saying that you maybe ran out of fuel after using only 117 litres?

[Harveyhall]

So it seems.  Filled it up after bleeding the lines etc and it took a total of 117 litres.

Thoughts. Looked at the tank today and it has 150 stamped on the black plastic

[Salty]

When you filled the tank after "running out," was the tank being filled at a high flow rate, followed by an overflow due to an airlock, but at which point you believed the tank to be full?
What is the gauge showing now, and how much have you used the engine and/or the heater since that fill up?

[Harveyhall]

Good thoughts on the high rate of fill. But the rate was slow and fuel was right to the top.
Gauge shows full and just filled 2 days ago, travelling 1/2 nm from the fuel dock.

[Craig]

On my 2010 model Bav 38 I have managed to put 146 litres in when gauge had been sitting on the empty mark for some time.

There are a number of factors to consider here.

1. I believe I got down to about 4 litres left without the motor cutting out, but that was in dead calm conditions. I know of a 2002 Bav 44 that had fuel cut out problems while heeling when they believed there was still a 1/4 to 1/3 of a tank of fuel left.

2. On my gauge I have 1/3 of a tank left when the gauge reads 1/2 full. My gauge appears to work well but is not calibrated properly. I have made a calibration chart by filling the tank from empty and recording how much fuel was put in when the gauge read , 1/4 full, 1/2 full, 3/4 full, full and also when actually full.

3. Never had the air-lock problem mentioned but heard of it occurring.

Craig
"Shirley Valentine"
Gold Coast
Australia

[Michael]

My recent experience is very similar to yours.
I recently purchased a 2007  Cruiser 33 that is supposed to have a 150 liter fuel tank. To ensure I had fresh fuel I decided to  run  the tank down to 1/4 before refueling.  I ran out of fuel when the gauge was reading just below half. I refueled and fuel gushed out of the vent after loading 119 liters. Thinking that the over flow could have been caused by a high delivery rate I returned some days later with a 20 liter container and was only able to add 2 liters before the tank over flowed.

The fuel tank is either not able to hold 150 liters, or the fuel draw off point is well above the lowest point in the tank. At a future date I will check the plumbing.

Clearly the fuel gauge is very inaccurate, this is  a challenge for another day.   

[JEN-et-ROSS]

The first time I decided to clean out our fuel tank in our B38 was about 10 years ago, it also gave me the chance to accurately measure the capacity - I was in for a shock !
   Having removed the inspection plate, (that also has the filler, fuel pick-up (& return), heater feed, gauge sender and vent attached) I pumped the fuel into jerrycans, so I now knew exactly how much I had removed. Then I cleaned the tank.
Now the interesting bit. I replaced the removed fuel and topped off the tank. I now know the tank only holds 90, yes NINETY litres.
   We were also told the tank capacity was 150 litres.
   The tank is under the starboard aft cabin bunk, GRP and glassed in. It takes up almost all the available space under the bunk so it couldn't be any larger. The only difference in our B38 and those Bavaria models mentioned above is that ours is a 1991 B38.
   

[Symphony]

90 litre tanks were common in older boats. Guess whoever told you 150l just assumed in the absence of documentation that capacities were the same as later boats.

[Lyra]

I think you should separate tank capacity, usable fuel and gauge display.
Starting from the gauge - it is practically useless. One should check over a period of time the actual liter/hour at cruising rpm and base consumption on that number and by recording fueling as accurately as possible (no problem at the marina, a bit less accurate when doing it at sea from a container, but then again the error is probably less than a liter).
The black plastic tanks are 150 liters.
From my experience, in the 150 liters tanks, even at less than 10 liters there is still fuel flow at a not so flat sea (no healing but a rough ride).

[JEN-et-ROSS]

90 litre tanks were common in older boats. Guess whoever told you 150l just assumed in the absence of documentation that capacities were the same as later boats.

     You're probably correct. We get around the problem by simply carrying another 80 litres in 4 jerrycans.
Incidentally, it was the previous owner who supplied the disinformation to the broker, but what the heck!, we love the boat and wouldn't part with it.

[Harveyhall]

Thanks for your replies. Nice to know I am not completely crazy. Our 1200 nm trip in June includes one section in and between islands on the Pacific West coast of Canada of 350 nm between fuel stops. Hoping there is wind but we will be carrying 3 x 23 litres of diesel to help ease the worry.

Dug to the bottom of the starboard locker to get clear idea of the tank and its setup. Took a could pictures.

Note: also fitting a new hour meter as the digital one with the 2005 instrument package is getting unreliable to read. (Always something)

[Lyra]

70 additional liters should certainly be enough. Made several passages of 350-400Nm with about that amount of extra fuel and it was enough even if had to motor most of the distance (mine is a 2004 B36 so fuel consumption would be about the same).
My hour meter also stopped displaying so I installed an hour meter at the navigation station - a simple electromechanical unit purchased at Ebay.

[Craig]

A Bavaria 38, no matter what vintage, should use less than 2 litres per hour cruising at 5.5kn.

70 litres should get you 180nm in relatively calm conditions without any sail assist.

Unless you are doing an ocean crossing or cruising a remote area, even a 90 litre tank should be sufficient.

Craig
"Shirley Valentine"
Gold Coast

[Sam Ward]

If you discover your tank holds just 90 liters, then you may have the same tank we have on our 2004 Bav 32.  The attached photo was provided by surveyor last Fall, but if you read upside down you will see that this tank is marked for 90 liters.  If you can't see your tank because it's glassed in then this is the tank you may actually have on board.

Does anyone have a more detailed description of about how to clean the tank once you remove the inspection plate and fuel?

[artemis]

Hi

I cut a hole in the top of my tank. But I think you could clean it through the sensor hole by removing the volume sensor and pumping out the tank then getting some kind of pump and sprayer (like a garden one) spray the inside with petrol Then pump this out  then spray with diesel and pump out.

This is I would think the best can do apart from cutting out this tank and installing a new custom fitted take what access hatch.

Im sure someone will elaborate on the above but this is what I would do.

Hope it helps

Mike
Artemis

[Craig]

Cutting holes in the top of polyethylene tanks can cause problems.

A friend had the spirals of plastic caused by the drilling caught in the Off/On switch.

I realise that European boats have more problems with Waxing and extra diesel bug because of the FAME added to the diesel than boats elsewhere but dozing the tank with enzyme ( Startron is probably the most common enzyme used) should remove any deposits. Keep in mind that Startron and other enzymes tend to only work when engine subjected to a long run where diesel is heated by the return line from the engine.

The solution to this problem used in Malta is to not worry about gunk in the tank. It is not a problem if you use an in-line strainer to catch the big bits before the Off/On switch. Boats more than 20 years old have never had tanks cleaned and never had a blockage, even though the strainers fill with debris. Their tanks are full of debris if they don't use an enzyme.

I'm cautious so I use a strainer and enzyme, and never had a problem since taking this action.

Craig
"Shirley Valentine"
Gold Coast
Australia