I have a 1993 Seaswirl 21 ft Striper with OMC Cobra Ford 5.0L EFI motor. In or out of water (with muffs on) you can increase power to 2700 RPM. After you reach this magical number the motor acts like it is goverened. Cuts in and out. Misses or surges. If you decrease throttle back to 2700 RPM works fine. Motor has run good up till now. Started to happen after a 2.5 hour run. If you stay below 2700 RPM runs good. Changed feul filters and verified no water in feul by pumping a gallon into a gallon glass jar and letting it sit. No water in feul! Had to return to base camp over open waters and rough seas barely on a plane. The normal 2.5 hour trip took 4 hours at slower speed. Anybody have any ideas?