30hp twin two stoke won't produce power.

[JollyRoger]

Hi, I have a 1997 30hp gmh twin cylinder single carb outboard that starts fine and runs at low revs fine but when the throttle is opened does not rev or produce power. Both cylinders show around 130psi. I have fitted new plugs, new CDI unit (power pack), Coils measure OK for Ohms, magneto coils and trigger coils physically look good and ristance measures good. The carburettor has been stripped and cleaned and appears to be fine (float height OK). The fuel pump appears to be OK. The engine has the same symptoms when operated out or in the water. When out of the water if the throttle is opened fully the engine runs rough and I guess only reaches half revs. The reed valves look new and seat properly. If the fuel supply is disconnected whilst running the engine does speed up momentarily before dying (which suggests electrics are OK?). I cannot see any problem with the carb. Any suggestions welcomed.