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Fuel Consumption

Discussion in 'Chris Craft Roamer Yacht' started by SteveD, Apr 14, 2005.

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  1. SteveD

    SteveD New Member

    Joined:
    Apr 14, 2005
    Messages:
    6
    Location:
    Sydney, Australia
    I recently purchased Chris Craft 56' and I trying to plan the deliver voyage. Can anyone give me accurate fuel consumption figures for this vessel which has 2 321HP Detriot Diesels.

    Bob Clinkenbeard in his article "Moving Twin Screws from R.I. to Savannah "
    Quoted the fuel consumption of his Roamer 56 as

    6.8-7.5 gallons per hour at 10-12 mph and
    8.5-10 gallonsp er hour at 19-22mph

    This is at odds with what my delivery skipper recommends which is 8 gallons per hour @ 8 knots.

    My skipper for the delivery wants to take on 4000 gallons of fuel (1000 in onboard tanks and 1500 each in Schultz IBCs in the saloon and aft deck) for a 2300 nm leg. This works out at 1700 gallons of fuel for contingency.

    I am worried about the stability of the boat with 6 tonne of fuel on the aft deck.

    I would like to be able to make the journey without the IBCs on the aft deck.

    Can anyone provide any extra information which could help resolve our difference of opinion.

    Regards

    Steve
  2. RSheaffer

    RSheaffer New Member

    Joined:
    Nov 30, 2004
    Messages:
    14
    Location:
    St. Croix River, Bayport Marina (MN)
    The Detroit Diesel website should have engine spec sheets that include fuel consuption data. I assume they're 6V71s. ??

    If not, contact your local DDC Distributor and ask for the BSFC curves on the model, rating of your engines.

    Good luck
  3. SteveD

    SteveD New Member

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    6
    Location:
    Sydney, Australia
    Sorry I forgot to mention they are 8v71s.

    I can't find anything on the Detroit Diesel web site relating to fuel consumption of the 8v71s.

    Most of the technical forums quote the fuel consumption of the engine based on HP. But how do I know how much HP is being produced by each engine when pushing the boat along at say 8 or 12 knots?
  4. RSheaffer

    RSheaffer New Member

    Joined:
    Nov 30, 2004
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    Location:
    St. Croix River, Bayport Marina (MN)
    Again, I'd call the Detroit Distributor. They should have BSFC (Brake Specific Fuel Consumption) curves that show consumption at a given RPM. If you know what the engines are turning (RPM) at 8 kts, should should be able to pinpoint consumption.

    You might want to have the Engine Serial Number(s) handy, as that will allow them to research the exact characteristics of that particular model, rating & vintage (fuel system).

    If they're like most engine Distributors, they should have a "technical support" hotline / desk. I show the company info as follows. (I'm sure there's one in Sidney ... I just didn't see it)


    MTU Detroit Diesel Australia Pty. Ltd.
    (Victoria - Melbourne)
    488 Blackshaws Road
    ALTONA NORTH, VIC 3025
    AUSTRALIA
    Tel.: +61 3 9243 9292
    Fax.: +61 3 9243 9271
  5. JimBauer

    JimBauer New Member

    Joined:
    Dec 15, 2004
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    22
    Location:
    Boat - Oakland, Home - San Diego
    As always I'm way far behind on the Roamer board, but here's my two cents. My boat has 8V71TI with small injectors for 390HP each.

    Looking at the consumption on my delivery voyage from Portland,OR to San Francisco about 18 months ago. This was about a 600 NM trip, I ran at about 13 knots and used just about a gallon a mile.

    I think your delivery captain is being conservative.... But, that's what they are paid for doing...

    Jim Bauer
  6. alloyed2sea

    alloyed2sea Moderator

    Joined:
    Jan 28, 2004
    Messages:
    850
    Location:
    Alex, VA
    I agree: aren't there any fueling points along the way?
    Even if you have to pay a bit extra, it would improve the stability me thinks.
  7. SteveD

    SteveD New Member

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    Apr 14, 2005
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    Location:
    Sydney, Australia
    I can't find any refueling spots between Ventura and Honolulu which is 2223 nautical miles. Do you know of any?

    Regards

    Steve
  8. SteveD

    SteveD New Member

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    Apr 14, 2005
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    Location:
    Sydney, Australia
    Progress Report

    Ashley has just left Honolulu. It consumed 2727 gallons for the first leg (from Ventura to Honolulu) of 2223 nautical miles. Not bad considering she's carrying an extra 12 tonne of fuel.
  9. Capt Keller

    Capt Keller New Member

    Joined:
    Dec 14, 2004
    Messages:
    50
    Location:
    Lorain, Ohio
    Once again I am amazed at the stability of these vessels. I too considered carrying extra fuel in the cockpit area for my trip home at one time. I'm glad I didn't have to, but it is nice to know that she could.

    Capt John S. Keller
    Great Lakes Pilot

    On a side note: As for fuel consumption; somebody gave me this formula, and it worked for me bringing my boat home. Take the square root of the hull's length at the water line, then multiply that by 1.15 for the vessel's most fuel efficient hull speed through the water. It may be possible to make that speed on just one engine with your boat without laboring as it was for mine. And one engine uses less fuel than two any day.

    for example: a fifty-six foot vessel is probably 53 foot at the water line. The square root being around 7.3. Times 1.15 would be around 8.4 statute miles per hour as your vessel's most efficient hull speed. Remember, I'm talking in statute miles per hour here not nautical miles per hour. So 7.3 kts would be your vessels most efficient hull speed also, not 8.0 kts. And one engine should be able to do that, don't you think?
    Last edited: Aug 2, 2005
  10. REBrueckner

    REBrueckner New Member

    Joined:
    Dec 8, 2005
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    2
    Location:
    Boat from New Rochelle, NY. Lately have been spend
    The DD Propeller Selection Guide, dated 7/69, gives "fuel -propeller load" consumption curves for the pleasure craft version 8V71 with N70 injectors . Here are a few points:

    RPM Fuel Consumption (gph)

    1200 4
    1500 6
    1700 8
    2000 12

    Remind the captain that if he does run low on fuel, he can throttle back to get better nmpg. 1700 gal sounds like a lot of spare fuel.