[Jim1]

Here are the numbers...Counter rotating engines...3000 rpm 20 mph port 3.9 gph starboard 3.7 gph, 3500 rpm 32 mph port 5.6 gph starboard 5.2 gph, 4000 rpm 35 mph port 7.5 gph starboard 7.3 gph, 4500 rpm 40 mph port 10 gph starboard 10 gph, 5000 rpm 48 mph port 13 gph starboard 13 gph. If I put throttles on the dash which I rarely do it would have maxed at 50 mph with just motors and little of boat in the water.
summary 3000 rpm calm water 20 mph @ 7.6 gph = 2.63 mpg.
3500 rpm @ 32 mph @ 10.8 gph = 2.96 mpg
4000 rpm @ 35 mph @ 14.8 gph = 2.36 mpg
4500 rpm @ 40 mph @ 20 gph = 2 mpg
5000 rpm @ 48 mph @ 26 gph = 1.84 mpg
Boat holds 135 gal so optimum range would be 399 miles in calm water which never happens. So range in 2 to 4 seas would be more in the range of 270 to 300 miles.
Check my math. A buddy of mine knows a group of Homeland Security guys who made a trip with Optimax, Yamaha four strokes, Yamaha two strokes. The 2004 optimax two stroke had the best fuel economy. I would choose reliablity over fuel economy any day offshore, but this series of Mercury's have never given me a problem.

Hope this helps,

Fryertuck

Hope this helps.