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Electronic tank gauge

Discussion in 'Ask A Hunter Owner' started by Secret sail, Mar 10, 2018. Add this thread to a FAQ

  1. Secret sail

    Secret sail

    Joined Feb 23, 2018
    3 posts, 0 likes
    Hunter 356
    Secret Fr Fr Marseille
    Hello from Marseille in France,
    I have just bought à 356. How accurate are the tank gauges? I don't intend running dry on diesel.... Just curious.
    Where Can I access thé diesel tank to inspect for sludge/bacteries?

    Great forum I have learn't loads already :)

  2. Bob R.

    Bob R.

    Joined Jun 5, 2004
    133 posts, 4 likes
    Hunter 356
    US Pasadena, MD
    Hello Secret Sail. I have owned a Hunter 356 for 11 years and sail it on the Chesapeake Bay. I have never relied on the tank gauges. Fortunately the 3 tanks that are monitored are all large enough to not have to worry about fuel, water or waste holding capacity. The diesel tank is easily accessible under the aft bunk and the holding tank is accessible in the starboard transom locker. The water tank is under the V-berth bunk and is not easily accessible.

    Where do you keep your new boat in Marseille? My wife and I are going to be in Marseille for a day on April 12 on a Viking cruise ship stop over. We will be in the Vieux Port (Old Port) area in the morning and plan to do some sight seeing along the water front and seeing some the older parts of the City. Is your boat far from the Old Port?

  3. JimInPB


    Joined Aug 22, 2017
    429 posts, 108 likes
    Hunter 212 & 170
    us Florida West Palm Beach
    The accuracy of a tank gauge is usually very good, but it depends on many things. For starters, when the sender is installed, it is common to bend the float arm to give the proper range inside a particular tank. Since this is usually done by hand, using only an eye as a calibration tool, the results can vary. Also, senders can suffer from corrosion as time goes by & loose accuracy.

    I constantly monitor the tank gauges when I fill the tanks on any boat, to see if the liquid that I put in matches with the change that I see on the gauge. If something looks funny, I immediately plan a time to take a look.

    Back when I flew planes, we never trusted fuel gauges. We always checked the wing tanks visually with a stick before taking off. If I plan to take a boat out past VHF range, I continue with this old habit of not trusting the gauge.

    The only gauge that I really trust is a sight glass. Sadly, that is not a viable option on most boats. Carrying a 5-gallon can of back up fuel is an option that often gives me comfort. In the case of a diesel, you will want to know how to bleed air out of the fuel system in case you do run it dry & need to reach for your can of back up fuel.

    Gauges usually work very well, until the day that they don't.

    JamesG161 likes this.
  4. JimInPB


    Joined Aug 22, 2017
    429 posts, 108 likes
    Hunter 212 & 170
    us Florida West Palm Beach
    Also, since the OP is in Europe...

    I think that the European sending units work backwards from the American ones. I need to look up the actual specifications to give accurate details, but if the gauge goes up when the liquid level goes down, you probably have a mismatch between the sender & the gauge, assuming that your wiring is good.

  5. JamesG161


    Joined Feb 14, 2014
    2,261 posts, 504 likes
    Hunter 430
    US Waveland, MS
    I do the same on my landlubber vehicles too.
    I have WEMA brand gauges that work on microswitch/float. Their precision is based on level change between switches.
    My 50 gal diesel gauge is ±5 gal and I keep 10 gallon in cans aboard.
    The difference between the two standards is USA has a "live zero". If my Europe standard ones, lose power then it reads like an empty tank.:frown:

    That is why they are reversed.

  6. Hunter Ad Bot

    Hunter Ad Bot

    Joined Oct 27, 2016
    0 posts, 9 likes
    US Seattle
    Hunter props, shafts, struts, and cutless bearings


    See the product

  7. Jerry Clark H356 SV Persi

    Jerry Clark H356 SV Persi

    Joined Mar 3, 2003
    606 posts, 37 likes
    Hunter 356
    US Grand Rivers
    I have a 2003 Hunter 356 bought new. I don’t trust the original gauges. I log every hour of my generator and Yanmar and use hours x rate per engine to give a total used. Keep records and you will find you can usually be within a half gallon or less at each refueling. Only time I was off much was when loaded very heavy and cruising. I also at that time had a worn Maxprop. My estimates were off. I now adjust for load and if offshore add .25 gallon per hour for wave action.

  8. senang


    Joined Oct 21, 2009
    12 posts, 0 likes
    hunter 38
    FR Monaco
    I do like Jerry. I keep track of engine hours after topping up. I cal it "tank hours". Being also in Europe I multiply by 3 (lt/hr) to get total litres burnt. As a rough guide on my H38, when the gauge says 3/4 I rneckon tank is half full, when gauge is 1/2 I reckon a quarter tank is left.

  9. chuckwayne


    Joined Mar 20, 2004
    1,363 posts, 27 likes
    Hunter 356 and 216
    US Portland, ME
    the 356 gauges are reasonably accurate if they are calibrated correctly -you can do that. The fuel gauge is not a float on an arm, it's a cylindrical tube gauge that MAY not go all the way to the bottom of the tank. Under the aft bunk you'll see an access hatch and the sender - removing the sender give you a 4" inspection/cleaning hole. I'm a "trust but verify" guy, I track run hours to calculate fuel use, and then I open the forward cover over the tank and shine a bright light into the tank. when you move the light up and down against the plastic tank, you can see the physical fuel level and get a good idea of the level.
    The waste and water tanks use external capacitive senders.

  10. Secret sail

    Secret sail

    Joined Feb 23, 2018
    3 posts, 0 likes
    Hunter 356
    Secret Fr Fr Marseille
    Thanks for all your comments and help. I sailed a Bénéteau 46 to Gibraltar once. 210 litres de fuel. Except the triangular tank prevents the fuel pick UP pipe going to the bottom. So 190 litres available... I am now very more cautious. I note the hours when I fill up. 3lit hour is about average for a yanmar3gm30. I carry 20 litres in à jerrycan in case :)

  11. JimInPB


    Joined Aug 22, 2017
    429 posts, 108 likes
    Hunter 212 & 170
    us Florida West Palm Beach
    On boats with installed fuel tanks, I usually make up a gauge reading sheet like the one below. This lets me check the accuracy of the gauge each time I fill up. It also gives me a good idea of what the reading actually means so that I can make more accurate fuel management decisions.

    I make the sheet up by starting with an empty tank, then taking pictures of the gauge as I put in measured amounts of liquid.

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