In one embodiment, a system for steering a marine vessel includes a first marine drive having a first engine control module and a second marine drive having a second engine control module, where the first and second marine drives are connected by a mechanical link. A first steer-by-wire steering actuator is configured to rotate the first and second marine drives to steer the marine vessel, and a first actuator control module controls the first steer-by-wire steering actuator. The system operates such that the first actuator control module activates the first steer-by-wire steering actuator if either the first marine drive or the second marine drive is running.