what is the range of this boat

If you are averaging 27 MPH and have a 103 gallon fuel tank, what is the range? I got a number, but it doesn't seem right.

At 27 mph your mpg should be 3.698 mpg and gph should be 7.28 giving a total range of about 380 miles or 14.15 hrs

That's what I got, but it just doesn't seem right based on use. But I haven't kept close track of fuel consumption.

Just like EPA car fuel mileage ratings, I wouldn't be surprised if the data shown on the chart is a might optimistic. Water conditions and boat loads could easily increase fuel consumption. Maybe take the numbers and downgrade 10-25% until you work out real numbers with your rig.

A strong headwind or a strong tailwind?
Big roller waves or flat water?
I would want at least a 50-60 mile safety reserve.

I don't think I would do anything over 150 miles round trip. The longest trip I've done in it was Summerland Key to the Marquesas. Was checking the numbers to see how we would do running from San Diego Bay to San Clemente Island.

The Yamaha would have to be running very inefficiently to get under 1.5 MPG.