Have Fundeck GS202 with a Yamaha 2004 F150 XTRC. Started losing top end speed at WOT. Sometimes the engine would surge to higher RPM. It has gradually gotten worse with max RPM about 4600. Idles fine. Runs OK at 3600 RPM. Changed fuel filter (no help), checked spark plugs (no black deposits), pulled fuel injectors (no sediment from small filters), changed primer bulb. I know there are two more filters but they are difficult to get too and one is internal. Took it back out and ran with the cowling off to see if the fuel filter maintained a levet. Watching the level in the fuel filter cup it ran just above the bottom of the visible part of the filter. I dont think this is normal and I am wondering whether this indicates a bad fuel pump. Any suggestions on further troubleshooting.?