I bought a pontoon baost in the winter with a 2003 Johnson 90 Hp 2-stroke on it....The first few times I took it to the lake I was very pleased with the motor and it ran excellent.....I went back over Memorial Day weekend and i noticed on friday that it was stumbling at high rpm's....Thought maybe it was bad gas....Boat did the same thing Saturday except it progressed to also cutting out a bit during takeoff and at high rpm's....On Sunday the boat ran fine for the 1st part of the day then it started cutting out almost al the time....Except for about a twenty minute period where it ran perfectly....To make matters worse I took it to a shop and they put a new fuel line on and adjusted everything....We also changed plugs....I was excited when I got to the Lake and it ran perfectly for about ten minutes then started cutting out and stuttering at high rpm's.Then it progreesed as it did over the w/ where I would have short periods of nothing wrong and then stumbling, reduced rpm,s and a sick sounding motor...The boat will not do this when in neutral when i rev the motor....Any ideas on possible problems or good repair shop in the southern/central ky area to help me solve the problem.

Thanks in avance