A boat control system detects a wire break status in a duplicated communication system. A hull of a boat is provided with a main remote control side ECU and a subremote control side ECU, and the subremote control side ECU communicates with an engine side ECU via the main remote control side ECU. Both of the remote control side ECUs are provided with storage buffers in which communication status confirmation data transmitted between nodes is stored. A broken wire detection section of the engine side ECU starts a determination when a system is started, and broken wire detection sections of both of the remote control side ECUs start a determination when communication status confirmation data is received from another node. Data indicating that communication is in an abnormal status is stored as an initial value in a main remote control data storage buffer.