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  1. #1
    SnaxMuppet's Avatar
    SnaxMuppet is offline Registered User
    Location : Saltash, Cornwall, UK, Europe, Earth, Milky Way, Universe (don't ask which one because I don't kno
    Join Date
    Jan 2006
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    Default Fuel Flow Sensor and Fuel Consumption

    Last week I fitted a fuel flow sensor to the boat. A Lowrance EP-60. This will give me accurate fuel useage info on my trip Round Britain. For those that don't know... it is a Merry Fisher 625 with a Suzuki 115hp outboard. Conditions were lively in Plymouth Sound but planeable but outside the Sound 1-2m sea and not planeable. Wind was easterly F4-5.

    Based on about 100 hrs of use last year I estimated that I used about 1 ltr per mile. After the first sea runs today I can confirm that I am using about 1 ltr per mile! [img]/forums/images/graemlins/smile.gif[/img]

    That did not come as much of a surprise but something else did... I was expecting that at displacement speeds I use less fuel per mile than when planing. Not so.

    The surprise was that I am using about the same consumption per mile either on the plane or off! 5kts showed about 5 ltr/hr, 15kts showed about 15 ltr/hr and 20kts showed about 20 ltr/hr.

    I do know that once on the plane then consumption per mile normally remains fairly stable until it nears WOT but I didn't expect that it would remain so at displacement speeds.

    I should say that in the range above 6kts until properly on the plane at about 15kts the useage dropped to anything up to 2 ltr per mile. This was not surprising.

    What does this tell me? I suppose it says that for my engine/boat configuration and in the conditions I had today, there is no benefit to either planing or not as far as fuel usage per mile is concerned as long as I don't operate between 5kts and 15kts.

    One thought... the propeller is quite a coarse pitch at 21" and I could imagine that it is not running efficiently at low speed. I will be trying the same tests with a 19" pitch prop next week so it will be interesting to see any differences.

    I have a lot more testing to do and if I find anything else surprising I will post.

    An interesting point though is that I felt a strange feeling seeing in figures how much fuel I have used instead of what is more normal at seeing how much is left... kind of emphasises how much it has just cost!! [img]/forums/images/graemlins/blush.gif[/img]

  2. #2
    Join Date
    Feb 2007
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    3,845

    Default Re: Fuel Flow Sensor and Fuel Consumption

    Interesting post, would be interested in knowing how the different props affects your fuel consumption (and performance).
    Had a fuel flow meter in the last boat (petrol) but tended to leave the cover on so I couldn't see it!!
    See the rainbow not the rain

  3. #3
    Join Date
    Jan 2004
    Posts
    312

    Default Re: Fuel Flow Sensor and Fuel Consumption

    I fitted a fuel 5100 something gauge to my 24 boat and found consumption at displacement speed was same as low speed planning,It was poor at just before planning speed and at Wot is was the best.

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