Abstract: Objectives At present, the IMO Second-Generation Intact Stability (SGISc) framework has moved beyond vulnerability criteria to the research of Direct Stability Assessment (DSA) and operational guidance, highlighting the need for direct assessment of the surf-riding stability failure mode arising from maneuvering-seakeeping coupling, Methods Using a RANS-based computational fluid dynamics (CFD) approach, combined with an overset-grid technique and a propeller body-force model, a six-degree-of-freedom (6-DOF) prediction method for instability motions of a self-propelled model in waves was developed. Taking the ONR tumblehome (ONRT) hull as the study case, the surf-riding phenomenon in regular following and stern-quartering waves at high forward speed was simulated, and the results were compared with published experimental data. Results The results show that, in calm water, the mean prediction error of propeller rotational speed across different forward speeds is 10.11%, and the mean error of total resistance is 3.13%. The wave conditions for the onset of surf-riding agree well with the experiments, and the computed maximum roll amplitudes exhibit the same trends as the measurements. Conclusions The study indicates that the propeller body-force simulation approach can successfully predict surf-riding at high forward speeds and is computationally more efficient than using a discrete propeller model. For the ONR tumblehome hull, as speed increases, the heave in the surf-riding equilibrium state becomes larger, while the pitch and roll angles decrease, and varying degrees of bow burying/shipping water are observed.