I intentionally ran at about 2/3 to 3/4 throttle to maximize fuel economy. I backed the throttle of of wide open to an engine speed that sounded quiet and smooth on the tiller. Data from my handheld Garmin. Going down river with the current: 33.2 miles, average speed 22 mph, 1 hour 32 minutes, considerably less than one 6.6 gallon tank. Going up river against the current: 32.1 miles, average speed 17 mph, 1 hour 53 minutes, slightly less than one 6.6 gallon tank. The overall average speed 19.5 mph.