I'm with sailhog on this. 200 miles in perfect conditions.
A yanmar 2gm (15hp 2 cyl) would burn about half to three qtrs of a gallon per hour at WOT. Variables would include sea state, wind speed and direction along with boat characteristics. Depending on the boat, you can do anywhere from 5 to 7 knots WOT.
(WOT=wide open throttle)
2007 Hunter 49