Port activity is assumed to be an integral part of maritime activity. Ships are supplied with water, food, fuel, electricity, spare parts and consumables when they are berthed in Ports. Therefore, the purpose of the service system is to reduce the waiting cost, from the time the ship’s arrival until its service. Delays in the system, and particularly in the queuing system, could occur due to irregularities in the ships’ arrival time causing uncertainty in time of service. On the contrary, a complex waiting system would require an increased commitment of capital for the construction and maintenance of appropriate infrastructure. As such an optimum size and operation of the port service system must be identified. To address this problem, this study presents a method for maximizing port administrator’s profit, by modelling and optimizing the waiting system based on Monte Carlo simulation techniques. Port of Piraeus is used to test the method. The case study assumes increased bunkering port calls due to the addition of an LNG refuelling station. The results showed that a range of 3 to 5 stations generate high profit while using too many service stations could lead to deteriorations of the profit.