A watercraft is equipped with an outboard motor and an inboard local area network (LAN) that communicates control signals to the outboard motor. An outboard motor operating device retains the ability to operate the outboard motor even if part of the inboard LAN develops an abnormality. In particular, a control signal that controls the outboard motor and a conditional information signal that indicates a condition of the watercraft are transmitted by independent cables that are mutually separated. Even if the cable for transmitting the conditional information signal or equipment connected to the cable develops an abnormality, transmission of the control signal for controlling the outboard motor is not hindered since the control signal is on the other cable, which is not affected by the abnormality. The conditional information signals are processed to generate and display return-to-port warnings based on the watercraft conditions and other operator issued constraints.