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    Fuel Flow-gctid345606

    I know this has been discussed before. But I am looking for some who has checked it out on a 3870 with twin 130 Chry. Mit. diesel engines. What is the best speed to use the least amount of fuel running both engines without the gen set, and running both engines with the gen set. The boat is a 1985 model.

    #2
    On ANY boat the most efficient speed will be slow.

    Look back at your wake. Think of the wake as wasted energy.

    KEVIN SANDERS
    4788 LISAS WAY - SEWARD ALASKA
    www.transferswitch4less.com

    where are we right now?

    https://maps.findmespot.com/s/36S4

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      #3
      According to David Gerr in his book "Propeller Handbook", the most fuel efficient speed is about 3/4 of the hull speed. This is about equal to the square root of the water line length in feet with the answer in knots. For a 38xx that would be six knots or seven mph. On flat water you might achieve up to four mpg.

      Your generator will probably burn about a quart and hour at light load.

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        #4
        rbmitchell wrote:
        According to David Gerr in his book "Propeller Handbook", the most fuel efficient speed is about 3/4 of the hull speed. This is about equal to the square root of the water line length in feet with the answer in knots. For a 38xx that would be six knots or seven mph. On flat water you might achieve up to four mpg.

        Your generator will probably burn about a quart and hour at light load.
        If you have an 8KW gen set, it will burn about 3/4 gal per hour fully loaded.
        Started boating 1965
        Bayliners owned: 26 Victoria, 28 Bounty, 32, 38, and 47 since 1996

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          #5
          rbmitchell wrote:
          .. the most fuel efficient speed is about 3/4 of the hull speed. This is about equal to the square root of the water line length in feet with the answer in knots.
          Probably the best way the see that is a good hull speed calculator.

          This is my favorite: http://"http://www.psychosnail.com/b...EED CALCULATOR
          Custom CNC Design And Dash Panels

          iBoatNW

          1980 CHB Europa 42 Trawler- "Honey Badger"

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            #6
            In my short time (1 yr.) with my 3870, running Mits engines, I found that around 1800 rpm, 8.5 knots gives me a good balance between fuel consumption & "time to get there". At that speed/rpm, getting about 2 nm/gal. If you slow it down as the previous posts suggest to about 6 kts, you'll be running about 1200 rpm and getting about 4 nm/gal.

            Hope this helps.

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