Ship Propulsive performance so far has been evaluated mainly in still waters. However, since ships are operated in actual seas with winds and waves, we should exert to evaluate propulsive performance in ship operating conditions. Seiun-maru, a training ship which belongs to Institute for Sea Training equips an automatic monitoring system for voyage data related on propulsive performance. This paper presents a method to evaluate a ship propulsive performance using voyage data gathering through a voyage round the world of Seiun-maru. The effects of natural forces such as winds and waves on the propulsive performance are estimated through the analyses. The reduction of propulsive performance due to natual forces is also estimated using theoretical and experimental methods. Discussions are carried out with comparing voyage and estimated data of propulsive performace.
