Most fuel thirsty one I ever ran was a 57' Viking Sportfish with a pair of 16v92 Detroits in her (yes, 16 cylinders). 1450 hp each. She would cruise at 31 kts and our fuel burn was 134 gals per hour with one of the two generators running. Ran her from Annapolis to Palm Beach for 4 years. Made 5 marinas real happy each way each year....
And my wife thinks I'm crazy for wanting to turn a C130 into a flying motor home I think the C130 would be cheaper to operate.