<p>An electric pump cycle rocket engine, which replaces the turbopump with an electric pump (ElecPump), is gaining attention due to its simplified configuration and easy ignition sequence. Although many studies have been conducted to estimate the performance of ElecPump for propellant supply, no prior experimental study on the hydraulic performance of an ElecPump with an unshrouded uni-impeller has been conducted. In this study, the hydraulic performance of a liquid methane ElecPump with an unshrouded uni-impeller was evaluated for a 3-tonf thrust class rocket engine. For this purpose, a pump test facility using water as a model fluid was established and hydraulic performance tests of the liquid methane ElecPump were conducted at both design and off-design flow rates. The test results at the design flow rate revealed that the head of the model fluid was up to 12.9% lower than theoretical predictions, which is attributed to fluid friction losses between the volute casing and the open impeller. Off-design tests were carried out within the range of 0.8 to 1.2 times the design flow rates, and the head and efficiency curves of the electric pump were derived. The pump head followed the affinity laws for rotational speed, showing trends similar to those of typical centrifugal pumps. Efficiency peaked at a flow coefficient of 1.1, regardless of rotational speed. An efficiency inversion was observed in specific low rotational speed regions, depending on the flow coefficient, which is presumed to be related to changes in electric motor efficiency based on the operating point.</p>