Marine and hydrokinetic (MHK) turbine development projects use power converters to convert harnessed variable power to grid compatible constant frequency AC. Using power converters in similar projects such as harnessing tidal energy through bi-directional rotor blades, or by using direct-drive technology for harnessing tidal and ocean wave energy, are rapidly expanding all around the world. However, power converters are known to have the lowest mean-time-to-failure among turbines’ components and have significant impact on increasing the cost of energy, especially at larger MHK turbine scales. This work proposes the potential of a novel MHK turbine drivetrain with three main modules. The first module is an “energy harnessing module” to harness variable hydrokinetic power. The waterwheel with a large catchment area is effective in harnessing low head, free flowing hydrokinetic energy. The second module is a novel “speed controlling module” that is a replacement of currently used power converters; it is the focus of this work. It produces a constant speed output from a variable input speed. Finally, the third module is the “power generating module” that generates grid-compatible constant-frequency electricity. The test results showed the superior performance of the proposed speed converter in obtaining constant speed frequency output from a variable input speed range.