Got my boat running the other day and took it out on the water it would only let me get about 1/3 throttle any more it would bog down and start backfiring. Ran around the lake a few times and then everything seemed to clear up still couldn't get full throttle but i was reaching speeds about 32 mph was getting ready to load the boat up and then it started acting up again. Couldn't hardly give it any throttle before it started backfiring. Things I have replaced recently are distributor, plugs wires, ignition switch, fuel filter and removed the anti siphon valve. I am starting to get very frustrated with this boat also put in new fuel with seafoam before last winter. I keep thinking it has to be something with the timing if anyone could help that would be great any ideas please.