Small, hydrokinetic systems generating between 0.5 and 10 kW of power allow for the potential of portable power generation. An optimized propeller turbine approximately 0.6826 m in diameter and a diffuser with an area ratio of 1.31 were used to produce a prototype for preliminary testing. The optimized diffuser augmented hydrokinetic turbine was investigated numerically to predict power and thrust curves for comparison during experimental testing. A gear box with a 10:1 gear ratio was selected for converting torque to angular velocity. A DC permanent magnet generator was selected for mechanical-electrical power conversion. At the ideal generator operating conditions consisting of a shaft rotation rate of 1150 RPM, a voltage of 48 V, and current of approximately 8 A, 375 W of power may be generated at a river flow speed of 1.5 m/s. Numerical predictions coupled with component efficiencies yield a system efficiency of approximately 0.61 before DC/DC conversion and 0.52 after DC/DC conversion.