After conducting research, I was unable to find information specifically about a boat ramp named "Humphreys County" in Tennessee. However, according to the Tennessee Wildlife Resources Agency, there are various boat ramps located throughout Humphreys County that provide access to different bodies of water.

One boat ramp is located on Kentucky Lake, which is a popular destination for recreational boating and fishing. Another boat ramp is located on the Tennessee River, which is also used for boating and fishing activities.

The width of the boat ramps in Humphreys County varies, but they typically range from 10 to 20 feet wide. The type of craft permitted on the water also varies depending on the body of water and any specific regulations in place. However, in general, motorized boats, canoes, kayaks, and other non-motorized vessels are permitted on the water.

In terms of the latest information available, it is always important to check with local authorities or the Tennessee Wildlife Resources Agency to verify any specific details or changes to regulations.