SteveK
Guru
- Joined
- Jul 5, 2019
- Messages
- 5,186
- Location
- Gulf Isalnds BC canada
- Vessel Name
- Sea Sanctuary
- Vessel Make
- Bayliner 4588
Kevin,Steve
In my 4788 I get very close to 2 NMPG at 7.5 knots. with each engine burning around 1.75 GPH at 1250 RPM.
If I increase the speed to 15 knots my consumption goes to around .6 to .65 NMPG as my fuel burn in the twin 330's goes to around 12 GPH each.
I have two ways of determining fuel burn. The first and most accurate is as you posted filling up the tank after a run at X RPM. The second is that i have flowscans installed. These are not perfect but give a very good measurement as well. I find the flow scans are more accurate at high RPM and engine loading than low speed BTW.
Your boat is the closest for my comparison. Your engines are 330, mine 250
I just filled my tanks to the brim, filled the same over one year ago.
Both engines 154.3 hours running, the GEN, the diesel heater on many occasion and the fuel replaced is 1574 litres or 416.4 US gal. My math 1574/154.3=10.20 litres per hour or 2.69 US gal per hour at an average speed of 7 knots.
That is 1.35 gph per engine which includes GEN and Heater.
Wait, the bolded you said 2nmpg @ 7.5 knots, that should be 7.5/2=3.75 GPH gallons but then you say 1.75 GPH. more confused. The 1.75 seemed like a good comparison.