This paper presents a wave excitation force prediction methodology for a slider crank power take-off system (PTOS) based on autoregressive filters. This study shows the feasibility of half period and zero crossing prediction of the irregular ocean waves to keep phase lock condition between the generator and the wave excitation force. This is critically important for unidirectional continuous rotation of the generator to maximize energy extraction. Results from the prediction with different filter orders are analyzed to accommodate real time processing requirements. It has been shown that 10th order filter provides the good compromise of accuracy and timely processing.