I have a 16FT Key Largo with a Suzuki DF70 (fourstroke) installed on a Bobs Machine Shop jack plate. The motor is stock except for a same size as OEM stainless prop and regularly use to be at 5000 rpm / speed was about 40-41 GPS. Twice I have had the motor at a local & often referenced Suzuki repair shop.<br />I had water in the fuel and it filled my fuel/water seperator which allowed water to pass (stoopid Tempo? brand crap). I emptied the entire tank and refilled with fresh gas. He has replaced all the filters and checked/tuned up the engine and the engine runs fine at idle and a little above. For some reason when I put it on the water it won't exceed about 3000 rpm WOT. This gives a speed of 14 MPH. The RPM does not seem to be limited by the engines computer (safety feature). When I raise the prop out of the water while traveling WOT 14MPH the engine instantly goes to pegs around 7000RPM and I drop the throttle and jack plate to slow the prop speed. It seems like it has no power with a load on the prop and we don't understand why.<br />I have removed the anti-siphon device and installed a new Racor fuel filter with the see-thru plastic contaminant check but performance didn't change.<br />I would liken the problem to be similar to the transmission slipping in your car. The engine is tuned and runs great but the greater the load and/or more performance you demand, the more the transmission slips. I know it's a stoopid analogy but it is the best description I got for my problem.<br />I'm checking for air leaks in the fuel lines now.<br />Any help or suggestions would be appreciated.