Impossible boat fuel mileage, 50 footer goes 29 knots at 5.5 liters per nautical mile??

Discussion in 'Powerboats' started by sdowney717, Oct 16, 2021.

  1. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    nautical miles liters.PNG Fantastic Boat Trip to Skellig Michael with John Brennan - YouTube

    at 7:14 into video, he shows the screen with speed and fuel consumption. Has twin diesels.
    at 5 minutes in, he says it is a semi displacement hull?
    How can this large boat go almost 30 knots per hour in the ocean using such small amount of fuel?
    5.5 liters is 1.4 gallons per nautical mile and the boat is going almost 30 nautical miles per hour.

    That is better mileage than many large boats get.
    What am I missing here.
    There are couple videos on this boat, one shows the layout and engine room.
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    5+ litres per nautical mile I would say isn't that wonderful.
     
  3. philSweet
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    It suggests around 450 hp at the shaft. Maybe a bit more if dead on the engine sweet spot. At about 45 pounds per hp at 30 knots, that's a 20,000 pound boat. A Sea Ray 500 weighs double that. It burns 47 gal/hour per engine at 28.6 knots. Maybe that's one engine? Or the 50'er isn't really a 50'er footer, and the tide is favorable.
     
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  4. sdowney717
    Joined: Nov 2010
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    sdowney717 Senior Member

    it is a 15 meter boat made by Redbay
    More detailed info and walk through on the boat at the dock.
    Meet The Owner : John Brennan - YouTube

    At 20 minutes in is the engine room. I think he says 3 Yanmar G70 engines?
     
  5. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell "Whatever..."

    That's ~160 litres per hour...
    Certainly not miraculous
    Also known as "knots".
    .
     
  6. philSweet
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member


  7. cracked_ribs
    Joined: Nov 2018
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    Location: Republic of Vancouver Island

    cracked_ribs Senior Member

    Seems reasonable, in the sense that I would have no problem with those numbers as long as it wasn't my visa we filled up on.

    Did you maybe get the units reversed in your head and think they were claiming 5.5litres per hour?

    Now that would be impressive!

    Although it could be done. I don't think with Yanmars but there's a Volvo product that could get you to 30 knots on a 20m boat, burning even less.


    Team-SCA-VO65.jpg
     
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