A system for controlling a marine vessel that includes a sonar depth finder configured to display a chart for a body of water. In accordance with the invention, the device further comprises: \u2014a near-end pitch estimation unit arranged for estimating the pitch of any near-end signal contained in the microphone signal and for controlling the post-processor unit in dependence of the estimated pitch such that harmonics of the estimated pitch may be substantially preserved. A filter device for improving the electromagnetic sensitivity is arranged in the housing. A fixing part is provided in the frame and the circuit section in order to fix the circuit section to the frame.