Click for Abeking Click for Mag Bay Click for Glendinning Click for JetForums Click for Westport

Fuel consumption

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

You need to be registered and signed in to view this content.
  1. Riva freak

    Riva freak New Member

    Joined:
    Feb 18, 2018
    Messages:
    4
    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

    Joined:
    Feb 29, 2008
    Messages:
    8,119
    Location:
    Miami, FL
    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

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    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

    Joined:
    Jun 22, 2009
    Messages:
    319
    Location:
    Long Beach CA
    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

    Joined:
    Feb 18, 2018
    Messages:
    4
    Location:
    New Zealand
    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

    Joined:
    Sep 8, 2004
    Messages:
    12,648
    Location:
    Satsuma, FL
    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

    Joined:
    Feb 22, 2011
    Messages:
    1,058
    Location:
    Long Island, NY
    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

    Joined:
    Sep 8, 2004
    Messages:
    12,648
    Location:
    Satsuma, FL
    Also check the prop.
  9. RT46

    RT46 Senior Member

    Joined:
    Feb 22, 2011
    Messages:
    1,058
    Location:
    Long Island, NY
    agree
  10. Riva freak

    Riva freak New Member

    Joined:
    Feb 18, 2018
    Messages:
    4
    Location:
    New Zealand
    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

    Joined:
    Feb 29, 2008
    Messages:
    8,119
    Location:
    Miami, FL
    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

    Joined:
    Feb 18, 2018
    Messages:
    4
    Location:
    New Zealand
    I agree. At 1750 rpm she is doing approximately 17 knots. She is planning.
  13. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    8,119
    Location:
    Miami, FL
    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

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    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

    Joined:
    Nov 14, 2016
    Messages:
    246
    Location:
    Holland, Michigan
    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

    Joined:
    Nov 10, 2019
    Messages:
    2
    Location:
    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
    Pizzazz7 likes this.