Flexible and fault tolerant networked steering system

A marine vessel steering system having a bus to which an autopilot interface unit (AIU) containing an autopilot function is coupled. The system having at least one steering location at which autopilot function controls are positioned and coupled through a cable (bus) interface unit (CIU) to the bus for communication with the AIU. In the event that more than one steering location seeks access to the bus, priority is established by an arbitration procedure between data frames transmitted from each steering location. A manual steering unit, such as a helm, is positioned at the main steering location and directly coupled to the AIU, wherein a switch selects between autopilot function rudder control and helm rudder control. Miniwheels, which operate in a manner similar to that of a helm, are positioned at steering locations remote to the main steering location which communicate with the AIU to switch between autopilot function control to miniwheel control. A multiplicity of AIUs may be utilized to maintain operation with a minimum of disruption should an AIU fail by switching from the failed unit to one of the other AIUs. Marine vessels containing more than one rudder have an AIU respectively associated with each rudder. Through a master/slave arbitration procedure one AIU is established as the master and the others as the slaves. After the master/slave relationship is establish, the master provides all data for rudder control.