2001 4- stroke 50 hp power loss

[captritter]

My engines starts up instantly sounds and runs awesome, but once the engine warms up i begin to loose power at WOT. Sounds like Im loosing a cylinders worth of power and engine begins to run rough. Still runs fine at lower speeds, but not past 3/4 throttle..... Only happens when engine gets warm it seems. Dont want to take back to mechanic and wait in line. What do you guys think???

[boats.net]

Can use a timing light to see if loosing fire on any cylinder, and need to run a fuel pressure test.