1998 Yamaha 150 surging 100-300rpms from 3600rpms-to wide open

[coachsorrel]

I have a 98 Yamaha 150 saltwater series model# s150xtrx. It start surging from 3600 to wide open about 100-300 rpms. While running the surging would eventually clear up. It has now gotten progressively worse. I have changed spark plugs, water and fuel separator, and cleaned the carbs. Went back to run it same thing. It starts out running fine and then gets worse as engine heats up. I kind of feel like the engine is misfiring. Cause when I speed up or slow down the rhythm of the miss does the same.
Can anyone please tell me what might be going on?

[jb123]

have you checked fuel pumps ?
ohm tested caps ?