The range of my 2008 21ec really varies depending on speed and conditions. For example, I brought it down the Delaware River and Northern Chesapeake on a calm day when the engine was breaking in (less than 50 hours) running at 8 knots which was maximum speed less about 400 rpm's (Yanmar recommends keeping the rpms high during break in), and I burned about 1.43 gallons/hour. After break in, I cruised at 6-7 knots and averaged about .67 gallons/hour. I've been figuring .75 gallons/hour for an average, and with 18 gallons in the tank (maybe 15 usable), that's 20 hours motoring on a tank. At 6 knots, that gives a usable range of about 120 nautical miles.