Starboard Engine will not rev up past Idle

[Speed]

Engine will start and idle, as soon as I go to advance the throttle lever the engine wants to die out. I rebuilt both carburetor's on both engines with no problems on the port engine. I had the same problem last year so this is the same issue before the carb rebuilds. Any suggestions would be helpful.

Twin Rotax 657x Engines
1995 Seadoo Speedster

 

[Bills86e]

Check your switch on shifter. They go bad.

 

[Speed]

Could this only cause one engine to not rev up or would this generally effect both engines?