1986 yamaha 115 outboard jumping 6k rpm to 5k rpm

[mlohara]

I just replaced the fuel lines and had the carbs looked at and replaced the spark plugs but my boat idels fine but when i give it full throtle it sometimes runs great a 6000 rpms then it will drop to 5000 rpms and stay there then it might kick and go back up too 6000 then back down to 5000 there is no certain time it does it, the engine can be hot or cold. Can someone please help.

[99yam40]

You can check for fuel delivery problems with a fuel pressure/ vacuum gauge teed into the line a different places too make sure there is not a restriction or sucking air with a piece of clear tubing.
If not the problem then I would clean the carbs and start checking the elect