Mustang,
There are two many variables involved to tell you precise mpg. I have a 28' glass cruiser with a pair of
fuel injected 260 hp
Marine Power V8's. I burn lots of fuel at cruising speed but have no fuel flow meter to keep a
record. With 150 gal. of fuel on board, I am comfortable with a 100 mile range. Friends with identical hulls and similar
power report averaging 1.15 mpg at
cruise. So you could expect around 2 mpg with a
single 260. Most
boating magazine tests show fuel
consumption in gallons per hour at a variety of RPM's .
Just follow the
rule of 1/3 of a tank out, 1/3 back, and keep 1/3 in reserve.