Several parameters influence the quality of the friction stir welded (FSWed) joints, such as tool rotational speed (TRS) and welding speed (WS). The present study investigated the consequences of these parameters on metallurgical properties of marine-grade aluminum alloy 5083 joints. As the heat generation increased, dynamic recrystallization refined the grain structure and significantly increased the hardness along the stir zone (SZ). Increasing the TRS of the welding tool increased the average microhardness value by 30.17% while increasing WS reduced it by 30.59%. Features like the arbitrary Lagrangian–Eulerian (ALE) formulation, adaptive remeshing technique, and mass scaling approach have provided a trustworthy and computationally effective FE model. The influence of TRS and WS on thermal history, residual stress prediction, and axial force variation has been thoroughly investigated. A comparison of experimental and numerical axial force variation reveals a 6% disparity between the two data sets. The results from the proposed numerically developed model matched well with the experimental trials.