Hard to say but my average speed is about 20-22kts, consuming between 9-10gph
So 40 hours at 10 gallons per hour is 400 gallons. Multiply by 4.5 litres per gallon = 1800 litres.
But this doesn't consider all the hours I've spend drifting with the engine at idle, or the time passing in and out of the harbour at 10kts or in the marina at 4kts, so I'd imagine the actual consumption will be a good bit less. For example, I know I haven't spent north of 3 grand in fuel, which is what 1800 litres would cost, so I know I can't have burned anywhere near that amount. Based on my visits to the fuel jetty I reckon I've spent less than a grand on fuel in 12 months.