This study aims to provide a clear relationship of how the storage status and duration of the urea affect the efficiency and performance of the SCR system. Focusing on the marine environment, the research compares NOx emissions using new urea solution versus urea solution stored for 5 years on ships. The results indicate that using new urea solution reduces NOx emissions by an average of 30%. Additionally, the study confirms that the impact of the SCR system on the combustion process is negligible. These findings the importance of regular urea solution replacement to optimize the performance of SCR systems installed to meet environmental regulations. Currently, there are no detailed procedures or regulatory standards for urea management and replacement on ships. Considering the strict NOx emission regulations and harsh storage conditions in ship, the study proposes the establishment of effective urea replacement cycles and management procedures.