Accurate measurement of the volumetric flowrate of working liquids is essential for process control, as well as energy consumption evaluation. Electromagnetic flowmeters have gained popularity in applications where low-pressure drop and low maintenance are required. Dwyer Instruments, Inc. recently developed an adjustable insertion electromagnetic flowmeter (IEF) featuring accurate and reliable measurement. However, unexpected and non-repeatable behavior in the K-factor was observed during the calibration process. The K-factor is the coefficient used to convert the measured electric potential to the flow velocity in pipes, and the non-repeatable behavior imposes challenges for precise measurement. A one-way coupled magnetohydrodynamics model was developed to reduce the effort and time of onsite troubleshooting and optimization. By modeling the measurement process, the transition of flow regimes and the regeneration of the boundary layer on the electrode surface were identified as the causes of the non-repeatable issue. Then, a series of parametric studies were performed to provide reliable solutions. A new design with further embedded electrodes to allow the smooth transition between boundary layers was recommended. The field test showed excellent repeatability by using the new design, and the non-repeatable issue was entirely resolved. The improvement in the IEF design was implemented in production in less than one week, and it reduced the calibration time by 50%.