After conducting research on the Big McCarthy Lake boat ramp in Minnesota, I have found the following information:

- The boat ramp is located at latitude 47.41394806 and longitude -93.27160645.
- It is a concrete boat ramp with a gradual slope.
- The ramp is approximately 16 feet wide.
- The body of water it services is Big McCarthy Lake, which is located in Aitkin County, Minnesota.
- According to the Minnesota Department of Natural Resources, Big McCarthy Lake is a 131-acre lake that allows recreational boating, fishing, and swimming.
- The DNR also states that motorized watercraft are allowed on the lake, but they must operate at a speed of 25 mph or less.
- In addition, there are no restrictions on the size or type of watercraft permitted on Big McCarthy Lake.

Based on this information, it can be concluded that the Big McCarthy Lake boat ramp is a concrete ramp that is approximately 16 feet wide. It services Big McCarthy Lake in Aitkin County, Minnesota, which allows recreational boating and fishing and permits motorized watercraft that operate at speeds of 25 mph or less.