John Deere or Cummins

Discussion in 'Diesel Engines' started by islands50, Sep 1, 2014.

  1. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    >I suppose it all comes down to how much power is required to push this vessel at it's hull speed, and or most efficient speed.<

    Probably not , usually sail boats are interested in hull speed but few marine motorists chose to operate there.

    The reason is slowing about 1K can frequently save 1/2 the fuel burn.

    Most cruisers will set up to load the engine well at a very good percentage of the 24/7 curve at cruise RPM.
    If the engine can operate at 70 hp at 1400, and the boat needs 60 at SL 1.15 , thats where you want to be.

    The shorter operating hour graph can be used for heavy weather when higher HP is required to maintain speed.
    Usually high speed in a sea state results in severe motions the operators find uncomfotible , and perhaps dangerous.

    The difficult boat to engine is the oxymoron , fast trawler, that may want 20K once or twice a year .

    Then the recreational ,short time , engine load is used for the top speed desired and a compromise is required the other 98% of the time when displacement cruising.

    Usually it only calls for lighter less efficient loading at higher RPM , so the vessel might cruise at 1800 rpm where it could put out say 110 hp , but the same 60 is needed to move the boat. A fuel map can help these decisions , prop load fuel burn is useless.

    The engine size , drive and hull should match the owners desirements , although efficient fast and slow may be wanted , a compromise is required.


    Most rec boats will not pay the bucks for a CPP or other fancy way to attempt to compromise .
     

  2. islands50
    Joined: May 2012
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    Location: Port Lavava,TX

    islands50 Junior Member

    Fred,
    I have to agree with you, and everything is a compromise these days, there again we must go back to my original post, the vessel is a troller, used for fishing, using west coast style tuna / salmon gear, maybe I should have said that to start with? Other then just describing a troller and assuming people knew what that was, and again I agree with you

    John
     
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