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Fuel consumption

Discussion in 'Riva Yacht' started by Riva freak, Feb 19, 2018.

  1. Riva freak

    Riva freak New Member

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    Feb 18, 2018
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    Location:
    New Zealand
    Hi guys. I have just purchased a 1979 superamerica 48. Maiden voyage bringing her home at average 17.5 knots. Just over 2 hours running. The fuel gauges read when we left between 1/2 and 3/4. First hour and a half running was great appeared to not be using much as needles hardly moved. Last half hour they dropped to just above empty? Hoping this is not accurate? Running twin Cummings 903. Could anyone enlighten me to a average litre per hour running cost please.?
  2. Pascal

    Pascal Senior Member

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    Fuel gauges, esepcially old ones, are usually inacurate. Dont rely on them! look up the fuel curves for your engines (online) then, fill the tank and keep a fuel log.
  3. olderboater

    olderboater Senior Member

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    Do you even know how much fuel your tank will hold? Fill it, run it, fill it again. See what you used. Between half and 3/4 to near empty tells one absolutely nothing, especially considering the gauges isn't likely accurate.
  4. Capt Fred

    Capt Fred Senior Member

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    Ditto to what was stated above. At that speed you would be lucky to get .5 NMPG, more likely .4. So my guess would be around 40 gallons per hour total.
  5. Riva freak

    Riva freak New Member

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    Thanks for your replies. I have now run a few tests different scenarios etc. She appeared to be running about 250-300 ltrs an hour at 1750 rpm. This seems very excessive considering we o my have 1000ltr fuel capacity? Starboard engine running clean with no smoke. Port engine running well with grey black smoke but not excessive .
    Ps. She has a clean bum and tabs working as they should.
  6. Capt Ralph

    Capt Ralph Senior Member

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    Port engine over fueling or is starving for air.
    Check air filters, exhaust leaks before turbo or the turbo itself..
  7. RT46

    RT46 Senior Member

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    just some suggestions.
    fuel coolers can dump fuel into exhaust
    or port engine can be overloaded/over fueled
    EGT can tell you a lot!
    also check tacs
  8. Capt Ralph

    Capt Ralph Senior Member

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    Also check the prop.
  9. RT46

    RT46 Senior Member

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    agree
  10. Riva freak

    Riva freak New Member

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    Props are good. New prop speed applied Nov 17. Checked a ok yesterday. I will head to boat today and check your advice thanks guys.
  11. Pascal

    Pascal Senior Member

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    That sounds like a very high fuel burn for a 48 footer. What speed are you getting at that rpm? Is the boat fully on plane?
  12. Riva freak

    Riva freak New Member

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    I agree. At 1750 rpm she is doing approximately 17 knots. She is planning.
  13. Pascal

    Pascal Senior Member

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    Is the bow high? Too much weight aft? Whats the hp rating on the engines ?

    Do they turn rated RPM flat out.
  14. olderboater

    olderboater Senior Member

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    How did you determine that?

    Also, only 1000 ltr fuel capacity? That seems extremely small for that boat. I wouldn't expect much range.
  15. 30West

    30West Member

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    If it has stock engines and props, at WOT it should be close to original RPM and speed. Check that first. If it isn't, look for drag (bottom fouling, added weight, wet core, rudder alignment). Have the engines checked well by someone factory trained and recommended. Has anything heavy been added or removed?
  16. jamed

    jamed New Member

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    naples italy
    she burns 120 l/h for engine at 2.100 rpm. in good botton condition at 2.100 she runs 22 knots. you are getting more 30 knots at 2.600 full rpm.
    she has 1.500 ltr capacity.
    look

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