Purifier is one of the separators used on ships to separate fuel from water and dirt in the ship's fuel system. The purpose of this study is to determine the factors that cause damage and efforts to overcome problems in the Water Distribution Device caused by O-rings damaged seal and Shaft System due to damaged spiral gear and bearing on the M.D.O Purifier at MV.Tanto Mitra. The research method used in this study is a qualitative case study method. Sources of research data were obtained from primary and secondary data, including observation, literature study, ship documentation, and interviews with technical personnel responsible for the maintenance of the M.D.O Purifier. The data obtained were then analyzed to identify problems and factors that influence its performance using Fishbone analysis. The results of this study indicate that the factors that cause damage to the Water Distribution Device and Shaft System in the M.D.O Purifier at Mv. Tanto Mitra lacks routine purifier maintenance, according to PMS. The operation does not comply with S.O.P and the lack of purifier spare parts and crew engine communication for purifier maintenance. Through optimal maintenance, it can increase the operational efficiency of the purifier, reduce the risk of disruption, and extend the life and performance of the purifier to remain optimal on a ship.