After conducting research, I was unable to find any information on a boat ramp named Gregory County with the given latitude and longitude coordinates in Nebraska. It is possible that the coordinates are inaccurate or the boat ramp no longer exists.

However, there is a Gregory Reservoir in South Dakota, which is just north of the Nebraska border. The Gregory Reservoir has a boat ramp that is managed by the South Dakota Game, Fish and Parks Department. This boat ramp is approximately 20 feet wide and allows for access to Gregory Reservoir, which is a popular spot for fishing and recreational boating.

The types of watercraft allowed on Gregory Reservoir are varied and include motorized boats, kayaks, canoes, and sailboats. There are no horsepower restrictions on motorized boats, but there are rules and regulations in place to ensure the safety of all individuals using the reservoir. It is important to note that boaters are required to have a valid South Dakota boating license and to follow all boating safety guidelines.

In summary, while there is no boat ramp named Gregory County at the given coordinates in Nebraska, there is a boat ramp at Gregory Reservoir in South Dakota that provides access to the reservoir for a variety of watercraft.