Propeller crashback refers to the sudden reversal of rotation by marine propellers. This maneuver results in large fluctuating forces that affect required propeller blade strength and maneuverability. Simulation methods that are adequate for propellers under design conditions are unable to predict crashback. We are developing the large-eddy simulation methodology to predict crashback. LES shows very good agreement with experimental results for amplitude and spectra of the loads, as well as the flow field around the propulsor.