Mercury optimal 115 issues. Please help me!!!

[Hopper]

My Dad bought a brand new tracker in 2013 it's has the optimax 115. I'm trying to help him out with this problem because no one can figure it out and bass pro won't do anything either..
Engine starts right up...always, no problems ever.
In neutral engine will rev right up, no hesitation no large amount of smoke. Runs beautifully..
come out of the no wake zone and this where the problems start.
engine will not run past 2000 rpm. 2100 rpm it shakes and sputters and looks like it's gonna leave the back of the boat all together. Throttle back to 2000 rpm runs perfect again
obviously bass pro shops had pop take it to a mechanic...4 times. Can't find any thing wrong with it, hung a new prop your good now, fouled plug runs perfect now.....bullshit. Bullshit. Bullshit
Dad is beyond done and doesn't know what to do...any ideas???

[grybrd]

First, do not rev this engine in neutral.
Second: serial number is critical to get engine specific assistance so please add it to your post.
Third: wait for competent help from the pros here and give pop a shot of patience. Taking the motor to the wrong mechanic 4 times has not been the solution but one does exist.

[EuropeanAM]

Welcome to BBC!

Please do provide your engine serial number- will be glad to assist once that is available.

DEFINITELY do not rev the engine in neutral (ever).

Also- are you hearing any Warning Horns???