A Nonlinear Model Predictive Controller (NMPC) for trajectory tracking of surface vessels which takes care of input saturation is designed based on a 3DOF dynamic model. NMPC calculates the future control inputs (propeller speed and rudder angle of the vessel) based on the present state variables by optimizing a cost function. The cost function incorporates input constraints as well as state errors in determining the control inputs is exploited. The identification tests are performed in an outdoor pool on a robotic boat which has an onboard PC104 computer and a navigation sensor. The data...