What affect does sea state have on fuel burn?

[Andy Bav]

I have only had my new boat a few weeks but it has fuel sensors. Coming back from Poole in about a F5 or F6 (much rougher than I prefer to be in) I noticed the fuel burn was around 5.0 when I would have expected it to be about 3.8 to 4.0.

So on that basis about a 25% increase in fuel burn. I also noticed that one engine was using more than the other but I don't know if this was a true reading or the gauges are not meant to be that accurate. One was using about 10% more than the other.

Not very scientific, but when we went from Swanwick to Poole via the Needles Channel it was pretty hairy stuff and we burned just short of a 1/3rd of a tank of diesel covering nearly a third of the journey (c33 miles). The next day it was flat calm after Poole Harbour entrance and the fuel gauge dropped from 2/3rd full to just below half by the time we reached Torquay.

One of the differences between the 2 days was that when it was flat, we could play around with legs and trim tabs (basically for something to do as it was quite a boring journey - but we got the fuel burn from 64 Lph to 54 Lph at same revs) but on the choppy day self preservation was more at the front of our minds and we trimmed the nose up higher - so as others have said, I guess attitude of the boat [and helmsman] in response to sea state will be a contributing factor as well

 

[Philiz]

I suppose a lot depends on what you term as "rougher weather"