The present invention relates to a system and a method for control and reduction of the RPM of at least one main engine of a vessel, which main engine drives at least one first propeller for propulsion, which first propeller is pitch-regulated, which second thruster propeller is pitch-regulated. It is the object of the invention to reduce the RPM of one ore more main engines of a vessel and by increasing the pitch of the propellers to maintain constant propulsion, and by reducing the RPM of the main engines to re-duce the fuel consumption and in this way reduce pollution. The object can be fulfilled by a system analysing the RPM and pitch of the first main shaft propeller, which system analyses the RPM and the pitch of the second thruster propeller, which system based on said analyses performs downward regulation of the RPM of the main engine.