A system for controlling a marine vessel's existing horn to automatically sound navigational signals as set forth in Coast Guard Navigation Rules, International and Inland for Sound and Light Signals for boats 12 meters 39 feet and larger, Rules 34 through 37. The system provides a user-interface with a selection of predetermined horn/light signals that can be repeated once or continuously via lights and/or sound, with a preview of the selected signal. The system permits a helmsman and other crew members to attend to other duties without constant attention to the vessel's horn, and enhances safety and Coast Guard compliance, and in the long term helps to inform and educate the operator through observing the signal patterns, on the water, or in boating courses like Coast Guard Auxiliary, Power Squadron and Community College courses.