In this study, the captive model tests and the free running model tests are carried out in order to investigate the stopping ability of ships. As a result, it is confirmed that the thrust deduction factor t and the lateral force coefficient Y'_<(P)> are function of J_S(=U_s/nD), and that their signs turn over according to J_s. And, it is led that if propeller revolution n changes stepwise, the stopping motion of ships is related to J_ <SRO>(=u_o/n_aD), and that non-dimentional stopping time and distance are function of J_<SRO>. Futhermore,it is confirmed that J_<SRO> decides whether ships turn to the right or to the left, and that taking account of machinery characteristics, ships tend to turn to the left. Finally, it is verified by the digital simulation of the stopping motion that the equation of motion using the effective thrust coefficient K_<T(1-0)> is useful.
