The Marine Master Clock System is designed to provide accurate time to date to all data logging and monitoring systems of vessels. The data of the NMEA from a GPS can be used to update the ship’s local time and then the master clock synchronizes automatically. To increase reliability, C-MOS IC is used in the frequency divider circuit. The robust mechanism provides a useful system for sailing vessels. The design of the system prevents vibration, shock, air compression or salty contamination. As slave clocks are installed in the ship, they will be adjusted to desired time according to the position of ship.