I took my boat out today and it ran great at first. At full throtle I was running about 5500 rpm, all of a sudden it drops to about 3000 rpm and then back to 5500 rpm over and over. If I would throtle back to about 4000 rpm it ran fine. Seems like a fuel problem. I swapped fuel tanks in case of water in the tank, I thought about the fuel filter. Any suggestions?