A method for monitoring drive shaft assembly load of a mixer machine of a mixer machine assembly during operation, the mixer machine assembly comprising: - a drive unit that is part of the mixer machine, said drive unit comprising an electric motor and a drive shaft assembly connected to and driven in rotation by said electric motor during operation of the mixer machine assembly, - a propeller that is part of the mixer machine, said propeller comprising a hub connected to a propeller shaft of the drive shaft assembly and a plurality of blades connected to said hub, wherein the propeller shaft extends in an axial direction and the blades extend in a radial direction, and - a control unit that is operatively connected to the electric motor, the control unit being configured for monitoring and controlling the operation of the mixer machine, the method comprises: - monitoring, by means of the control unit, a drive shaft torque (Tz) about a drive shaft of the drive shaft assembly, the method is characterized by the steps of: - determining, by means of the control unit, an average drive shaft torque range (ATzR) based on at least one drive shaft torque range (TzR), wherein each drive shaft torque range (TzR) is equal to the difference between the highest drive shaft torque value (Tz max) about the drive shaft and the lowest drive shaft torque value (Tz min) about the drive shaft detected during a predetermined angle of rotation (α) of the propeller during operation of the mixer machine assembly, and - comparing, by means of the control unit, the determined average drive shaft torque range (ATzR) with a predetermined torque range limit value (TzR limit). - a drive unit that is part of the mixer machine, said drive unit comprising an electric motor and a drive shaft assembly connected to and driven in rotation by said electric motor during operation of the mixer machine assembly, - a propeller that is part of the mixer machine, said propeller comprising a hub connected to a propeller shaft of the drive shaft assembly and a plurality of blades connected to said hub, wherein the propeller shaft extends in an axial direction and the blades extend in a radial direction, and - a control unit that is operatively connected to the electric motor, the control unit being configured for monitoring and controlling the operation of the mixer machine, the method comprises: - monitoring, by means of the control unit, a drive shaft torque (Tz) about a drive shaft of the drive shaft assembly, the method is characterized by the steps of: - determining, by means of the control unit, an average drive shaft torque range (ATzR) based on at least one drive shaft torque range (TzR), wherein each drive shaft torque range (TzR) is equal to the difference between the highest drive shaft torque value (Tz max) about the drive shaft and the lowest drive shaft torque value (Tz min) about the drive shaft detected during a predetermined angle of rotation (α) of the propeller during operation of the mixer machine assembly, and - comparing, by means of the control unit, the determined average drive shaft torque range (ATzR) with a predetermined torque range limit value (TzR limit). - monitoring, by means of the control unit, a drive shaft torque (Tz) about a drive shaft of the drive shaft assembly, - determining, by means of the control unit, an average drive shaft torque range (ATzR) based on at least one drive shaft torque range (TzR), wherein each drive shaft torque range (TzR) is equal to the difference between the highest drive shaft torque value (Tz max) about the drive shaft and the lowest drive shaft torque value (Tz min) about the drive shaft detected during a predetermined angle of rotation (α) of the propeller during operation of the mixer machine assembly, and - comparing, by means of the control unit, the determined average drive shaft torque range (ATzR) with a predetermined torque range limit value (TzR limit).