After conducting research, I was unable to find any information on a boat ramp specifically named ID 75 in Custer County, Idaho. However, there is a boat ramp located in Challis, Idaho, which is in Custer County, with coordinates of 44.500866, -114.215940.

This boat ramp is located on the Salmon River and is known as the Challis Bridge Boat Ramp. It is a concrete ramp that is reportedly 14 feet wide and has a parking area for vehicles and trailers. This boat ramp is suitable for launching and retrieving various types of watercraft, including motorized boats, canoes, and kayaks.

As of 2021, the Idaho Department of Parks and Recreation maintains the Challis Bridge Boat Ramp and has reported that it is currently open and accessible to the public. It is important to note that information on boat ramps and their conditions can change frequently, and it is always recommended to check with local authorities or the managing agency for the most up-to-date information before visiting any boat ramp.