I had the same problem in Johnson V4 90hk 2-stroke 2006. The problem was caused by the warped float bowls of carburettors. By changing them and the gaskets the problem will be solved. Symptoms were that the engine did not take full RPM and it was (sometimes) stalling. There could be weeks of operation without any symptoms, and then they started again. Warped bowls cause air leak to carburettors intake and the engine does not get enough fuel. Engine started and idled fine and was running ok up to 3000 rpm, but started run unevenly with wide open throttle.
Antti
