Ocean Renewable Power Company's (ORCP) RivGen device is a horizontal cross-flow turbine featuring a proprietary power takeoff unit. This system has been proven in real-world conditions in Alaska and is now the longest operating hydrokinetic project in the Americas. ORPC systems typically use direct drive permanent magnet (PM) generators which are highly efficient, but large and relatively costly. To reduce cost ORPC has identified several geared PM generators that may be suitable as replacements, however the efficiency of these components has not been evaluated across a range of operating conditions. The data included here were derived from dynamometer testing of a candidate replacement generator for RivGen, installed a deployment-ready, submersible enclosure and all relevant mechanical components. The candidate generator was an EMF Synchronous Torque Motor (model SQM200-500) with a rating of 18.8 kW. This model is a permanent magnet, direct drive generator with magnetic gearing. It was installed on a dynamometer equipped with a Siemens 1FW3202 torque motor (rated for 500 Nm and 150 RPM under continuous operation) driven by Siemens Sinamics S120 components. The dynamometer has an inline torque cell and encoder to measure shaft torque and speed applied to the candidate power takeoff. Shaft speeds between 10 and 100 RPM and torque values up to 1750 Nm were mapped within the limits of the prime mover and motor module's capabilities included added set points achieved with a 5:1 gearbox. The data here include raw and processed data products from all relevant tests. These data products are included in .xlsx files. All of the raw data can be selected from those the different sheets in the Excel files and imported into any program for additional processing. A Python script (Jupyter Notebook, .ipynb) is also available remake plots of the processed data products.