This is conjecture and for discussion only. Assume you have a flat bottom boat with 700 lbs load and a 20 HP engine. At 3 mph you will get about 14 mpg. At 6 mph about 12 mpg - at 9 mph about 2.5 mpg - at 12 mph the mpg will increase to 10 mpg - at 15 mph it will drop to 8.5 mpg - and at 21 mph it will drop to 2.5 mpg again. I wish I could graph this as it would make a lot more sense, but the whole idea is your boat will be more efficient at hull speed and below. It will be least efficient as it climbs the bow wave or runs at max speed.
A properly tuned 4 stroke internal combustion engine will burn about .5 lbs of fuel per hp, per hr at WOT.
Example 15hp x .5 = 7.5lbs fuel per hr at WOT
Egret 16 has a 41 gallon fuel tank,
at 55 mph that gives you a range of about 190 miles
Throttle back to cruising speed and you'll probably get 250 mile range.
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