fuel burn for Cummins diesels in a Sundancer 390

Discussion in 'Sea Ray Lifestyle & Cruising' started by Dan G, Nov 17, 2017.

  1. Dan G

    Dan G New Member

    4
    Nov 17, 2017
    2005 Sea Ray Sundancer 390
    Cummins QSB
    Hi - My wife and I are planning to do some long distance cruising, FL to ME next summer, and possibly the Great Loop in a year or so, in a 2005 Sundancer 390 with 380 hp Cummins QSB 5.9 diesels with V drives. I'm having a lot of difficulty finding gallons per hour and gallons per mile data at various rpms and cruising speeds for the 390 with Cummins diesels. Finding a lot of info on the gas engines, but none on the diesels. Can anyone point me in the right direction, or provide any anecdotal info? Thanks.
     
  2. alnav

    alnav Member GOLD Sponsor

    768
    Sep 16, 2009
    West River, MD
    40 MY
    QSB 425
    Here is a link to a copy of the Cummins Marine Performance Curve sheet: https://www.sbmar.com/docs/performance-curves/QSB 5.9 [380,3000,8464,HO,May 10,M-91364].pdf.

    The engine is going to perform the same in terms of fuel burn vs. RPM no matter where it is installed and the linked sheet provides those data. Now you need to know the speeds for your boat associated with a given RPM. Hopefully an owner has constructed a table and will pass that on but you could also do this yourself if you're able to do some speed runs.
     
    Dan G likes this.
  3. Dan G

    Dan G New Member

    4
    Nov 17, 2017
    2005 Sea Ray Sundancer 390
    Cummins QSB
    Thanks! I am in contract to buy this boat - survey and sea trial coming this week -so I don't yet have the ability to create a performance table for the 390. Hoping someone already has, and will pass it on. Anyway, appreciate your response.
     
  4. Tman

    Tman Member SILVER Sponsor

    248
    Aug 10, 2012
    Seattle, WA
    2014 Sabre 48 Salon Express
    Twin Cummins QSC 550
    Zeus Pod Drives
    Dan - I use to own a 2005 390DA w/380 QSB's and have a slew of performance data that I captured. Re-propped to dial in exactly where I wanted her performance to be. Attached is a table I plotted which you may find useful. I can also advise that based on how I ran her, the average fuel economy I was getting was 0.96 mpg. This is average over the some 900 hours I had her.

    Tom
     

    Attached Files:

    Dan G likes this.
  5. Dan G

    Dan G New Member

    4
    Nov 17, 2017
    2005 Sea Ray Sundancer 390
    Cummins QSB
    Thank you, Tom. I'm not sure I'm reading this correctly. Just to clarify, with the new props: @ 1800 rpm you made about 10 kts, burning about 13 gph; @ 2200 rpm you made about 15 kts, burning about 20 gph; and so on. Am I reading this right? Let me know, and thanks again.
    Dan
     
  6. Tman

    Tman Member SILVER Sponsor

    248
    Aug 10, 2012
    Seattle, WA
    2014 Sabre 48 Salon Express
    Twin Cummins QSC 550
    Zeus Pod Drives
    That is correct Dan. You will see much reference in the various forums about making sure your vessel is propped correctly. That is to achieve the WOT ratings the engines should. I sized my props such that at WOT, the resulting RPM maxed out at the limiters for the QSB something like 3060 or 3080 I believe (its been a while for me) and the engine load at that WOT condition was showing 95%.
     
    Dan G likes this.
  7. UnleashedBeast

    UnleashedBeast New Member

    17
    Nov 21, 2017
    Pensacola, Fl.
    Shopping for a Sundancer or Sedan Bridge with Cummins diesels.
    Boatless
    Subscribing to this thread, as I have also decided the 390 with Cummins QSB might be the perfect boat for my wife and I.
     

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