I have a 1997 271 Fastech. The boat was running fine a year ago, but today when I took it out it would not rev above about 2000 rpm when in gear without stalling. In neutral there was no problem - revved it to 3000 rpm without any hesitation. But under load it will stall.Could it be a blocked fuel filter? Mechanic told me to replace it after last service (a year ago) because the fuel tank had some rubbish in it, but have run the boat very little and thought that it could be run some more before replacing the filter. But are these the symptoms of a clogged fuel filter? Any help much appreciated. Engine is 454 Magnum MPI.