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Fuel economy at trawler speeds

Discussion in 'Post Yacht' started by madmikec, Aug 9, 2016.

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  1. madmikec, Aug 9, 2016
    #1
    madmikec

    madmikec New Member

    Joined:
    Aug 9, 2016
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    2
    Location:
    old saybrook ct
    Hello all,

    This is my first post on here as my live aboard boat search has brought me to reconsider the possibility of a Post 42. I'm most interested in what the fuel burn is like in the trawler speed range (less than 10kts?). I've been looking heavily at trawlers so that I could find something economical to cruise in as a 25 y/o living aboard and cruising around ct/ri/ny and not break the bank every weekend. My trawler search has left me concerned that they lack the power IF NEEDED if caught in a nasty beam sea or a strong river current. So, if I were to look more at the 35'-45' sport fish market:

    1) Could I cruise at trawler speeds with similar fuel burn numbers and benefit from having the extra power when I need it?
    2) Will it be harmful to run the engines at these speeds for a 3-6 hour cruises?

    Any feedback is greatly appreciated, thanks!
  2. Capt J, Aug 9, 2016
    #2
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
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    14,435
    Location:
    Fort Lauderdale
    1. Yes you can. You'll see around 1.5 mpg at trawler speeds in a 35'-45' SF. However you might want to call it trolling speeds (some fisherman might get offended otherwise) heehehe. Most SF troll for 6+ hours when they go out fishing normally.

    2. You are going to run them up to cruise for 30 minutes every 4-6 hours to clean them out, if only a 3 hour cruise run them 20 minutes at cruise on the way in, if a 6 hour cruise run them up for 30 minutes on the way in.
  3. Pascal, Aug 9, 2016
    #3
    Pascal

    Pascal Senior Member

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    Miami, FL
    In addition to what J said, keep in mind "under 10kts" will result in huge differences.

    Generally speaking, the hull speed of a boat is the sq root of the LWL (waterline not LOA) times 1.3. So figure LWL 36' for a 42 footer, means hull speed will be about 7 to 7.5 kts.anything over that and your fuel burn will go up exponentially... Worst case scenario.

    So if you hold it around 7kts, then your burn will likely be around 5 0r 6 GPH. Push it to just 8kts and it will likely be around 10gph. By the time you hit 9 kts, my guess sill be 13 to 15gph... Basically twice the burn for 30% speed.
  4. madmikec, Aug 12, 2016
    #4
    madmikec

    madmikec New Member

    Joined:
    Aug 9, 2016
    Messages:
    2
    Location:
    old saybrook ct
    Thanks you both for the info -

    The search is definitely more open to an older sportfish now...