Yamaha 60 4 stroke 2005 bogs over 4000rpms

Hi, I need some help.

Long story short. I bought my neighbors boat because he never used it. (first mistake.)
At 4000 rpms it will run all day. If I punch it, it will die within a few minutes.
I've replaced:
Fuel lines
Sqeezeball
Anti syphon valve
gas
both fuel pumps(with vst tank)
injectors
fuel filters
water separator
I have even run with an external 3 gallon tank to confirm it isn't my gas lines.

I don't know what else could cause this. It feels like it is starving at this rpms.

My mechanic is looking into another trade after dealing with this motor.

Thanks,
Jackson

 

Thoughts,sitting around-the carb is probably all gummed up:
-high speed jet-clogged,damaged?
-timing

 

Take it to a yamaha dealer. They should be able to fix it straight away.

 

Hi, Thanks for the replies.

I have taken it to the yamaha dealer. He swears it is fuel related but I don't know. I have replaced everything he has recommended. It is an injected engine so no carb. I was just wondering if someone else has experienced a similar problem.