Re: Fuel range????Help.
Much like flying, the current or wind working against you will decrease fuel economy...you still move 1 mile through the water (air), but the water (air) itself has moved you back (for example)2/10ths of a mile. If rpm remains constant, yes, fuel used in gallons per hour will remain constant, but your forward motion relative to the land will vary with headwind/tailwind, so miles per gallon will vary. Perhaps better to figure gallons per hour used at different power settings, then calculate the desired distance. You can then monitor your progress (fuel consumed/distance attained). A starting point is one-half pound of fuel used per hour per horsepower, remembering that engines are most efficient at/near power peak. Therefore, a 200-horsepower motor should consume about 100 pounds of fuel per hour at WOT, or, with fuel around 6 lbs/gallon, (100/6 or) 16.666 gallons per hour. This should be fairly constant; the amount of miles travelled on that 17 gal/hour is not a constant but will be determined by weight/size/efficiency of hull, prop pitch/size, and the variables of current. At lower power settings, the rules still apply; if you are using only 100 HP (not to be confused with 1/2 throttle!) your fuel usage should be closer to 8 gph, but your speed in mph should be more than 1/2 your WOT speed. (In general terms, to double the speed generally requires quadrupling the horsepower; this is due to drag).<br /> Clear as mud? Good luck!
Think about it. If your driving down the road with a head wind(foul current)your mpg goes down. If your driving down the road with a tail wind (fair current)your mpg will increase. When you're figuring your distance based on fuel on board your not allowing yourself any cushion.