After conducting research, it appears that there is no boat ramp named O'Brien Reservoir in Minnesota at the provided coordinates. However, there is a boat ramp at O'Brien Lake in Minnesota, which is located at latitude: 47.2861° N, longitude: 93.3614° W.

According to the Minnesota Department of Natural Resources, the boat ramp at O'Brien Lake is a concrete ramp that is 20 feet wide. It services O'Brien Lake, which is a 299-acre lake located in Crow Wing County. The lake has a maximum depth of 46 feet and is primarily used for fishing and recreational boating.

The DNR states that motorized watercraft are allowed on O'Brien Lake, as well as canoes, kayaks, and other non-motorized watercraft. However, there are no wake restrictions on the lake, so it is important for boaters to be aware of their wake and ensure that they are not causing damage or disturbance to other boaters or shoreline structures.

It is important to note that the information provided is accurate as of the time of research and is subject to change. Boaters should always consult the latest regulations and guidelines from the Minnesota DNR before launching their watercraft.