Internal combustion engine (ICE) is the most important part in vehicle. Generally, the combustion of ICE is facilitated by petrol and exhaust gas emission from vehicles is a primary contributor to the environmental pollution problem. In this research, Plug-in hybrid electric recreational boat (PHERB) is introduced and PHERB has a combination of energy storage system, ICE and electric machine. The objective of this work is to derive a detailed model of ICE in MATLAB/SIMULINK environment, develop proportional-integral (PI) controller for ICE and optimize ICE using a Genetic Algorithm (GA) based on PI controller. The efficiency of ICE for PHERB obtained was 40 % at rotational speed 4000 rpm of the engine. Via using the GA, the optimal performance of ICE is found by power demand curve, as a reference for the model with mutation probability used is 0.085. In terms of the performance results, the optimal tuning parameters of ICE for PHERB had a significantly improved performance towards green and clean technology.