I'd bet my life on this in a rough sea with a tough ride you will be able to cover 237 miles ....in fairer 274 miles in optimum conditions flat seas and running at 3800 rpm at 22-25 mph i'd bet on 288 miles
i always figured on 1 mpg with my 2530 because i knew if i got in the real sloppy stuff i was slugging it out at .8mpg and if it was nice 1.2 to 1.4 depending on load. Which is part of the reason I added a second fuel tank to my boat for an extra 90 gallons. I looked into the fuel bladders and just didnt like the idea and since i did so many long trips it made sense to me to add another tank.
A trip from Nantucket to Atlantis- Veatch is 200 miles round trip, Ive done the numbers but thats just on paper. my normal cruse at 4200 I make 1.2 mpg. I hold 250 gallons of fuel. I was looking at buying a bladder, do you guys think I need one?
200 round trip you should be fine even if its real snotty and youre getting .8 youd be right at 200 miles on 250 gallons which im assuming if it were that rough you wouldnt be going anyways. You could also bring a couple 5 gallon jugs and just dump them after you run out there 20 gallons would be more than enough. bladders are expensive and i personally dont like them for smaller boats. id add another tank before a bladder if you are worried about range.