yamaha help please

[onewareagle]

i have an 06 150 four stroke that after running for 10-15 minutes it is impossible to run at full throttle which having a jet foot is usually around 51-5200 rpm if you pull back to around 48-4900 rpm it clears right up but any bit of throttle past that and the motor goes crazy cutting out busting up.i carried it to the marina they added a fuel/water seperator said they did a lake run on it and was ok.but the first time i carried it to the lake i left the ramp it ran fine about 15 minutes later and for the rest of the night i had constant problems especially gunning it out of the hole it sounded like an old hit and miss motor from back in the day.i am considering buying the diag. software from sims and checking it out on the water myself i just don't know if i need to do that yet,on the other hand i spent 350 dollars on fuel filter and a lake test that has yielded no results.any ideas or experience with this would be greatly appreciated

thanks, onewareagle