But assuming that he's doing at least 30 mph for that 10 gph fuel rate,
that's still 3 mpg... For a boat, anytime your fuel consumption is measured
in "miles per gallon" instead of "gallons per mile", you're doing good...

Since these boats are generally used for "point A to point A" travel (with no
particular destinations in between) and the trip is designed to take "X" number
of hours, fuel consumption is a factor.