fuel burn for Cummins diesels in a Sundancer 390

Dan G

New Member
Nov 17, 2017
6
Boat Info
2005 Sea Ray Sundancer 390 DA
Engines
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.
 
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.
 
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.
 
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
 

Attachments

  • Prop Curve for Ruff Seas Rev1.pdf
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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
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
 
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%.
 
Subscribing to this thread, as I have also decided the 390 with Cummins QSB might be the perfect boat for my wife and I.
 
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
Do you still have the raw numbers (excel) for the 390 ?
I have 21 x 23 NIBRAL props, though not sure what brand (PO painted them with some gray paint) and getting them scanned over the winter. However, I'm debating the pitch change as long as they are in the shop. Don't have much data for my own boat as it was new in August 2021 for me.
TIA
 
All boats are different. You really need to go out and make your own chart.
 
I have a 2005 390 with Cummins QSB 5.9's. Boat was over propped with 21x23 props. Had to reduce pitch to 21x21 1/2 to get close to the Cummins fuel burn chart.
 

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