Marine vessel propulsion system, communication terminal, and keycode server

A marine vessel propulsion system for applying a propulsive force to a marine vessel, the marine vessel propulsion system comprising:

• a propulsive force generator to generate the propulsive force;
• a drive source to drive the propulsive force generator;
• and
• a controller configured or programmed to control the drive source to perform a plurality of marine vessel maneuvering-related functions including at least one limited function;
• wherein
• the controller includes an interface;
• and
• the controller is further configured and programmed to include a restriction unit to restrict a control operation for the at least one limited function, and a restriction cancellation unit to cancel the restriction effected by the restriction unit to permit the control operation for the at least one limited function when a predetermined keycode is inputted from the interface or is registered in the controller.