That's part of the problem, he doesn't know. The guy he bought the boat from passed away the day Eric bought it and there is no one else who knows the boat well. So he doesn't know how fast she'll go and what the burn rate will be.
He was told what the fuel burn was at 9 knots, that's the speed the previous owner ran at all the time. But no captain of a party boat in their right mind would ever attempt a 150 mile trip without positively knowing what the burn rate is. Would you take someone else's word for it and chance being stuck 80 miles from home?
Ok so now he knows what it burns @9knots before he didnt Its a start