After conducting research, I was unable to find specific information about a boat ramp named State Highway 1804 Emmons County in North Dakota. However, I did find information about a few boat ramps in the general area.

One boat ramp in Emmons County is located on the Missouri River, which services a variety of watercraft including powerboats, sailboats, kayaks, and canoes. The width of this boat ramp is unknown. Another boat ramp located in the same county is on the east side of Lake Oahe, which is a popular spot for fishing and boating. This ramp is roughly 20 feet wide and can accommodate boats up to 25 feet in length.

It's important to note that regulations and restrictions for watercraft can vary depending on the body of water and any state or local laws. It's always best to research and follow any guidelines or rules that apply to the specific location you plan to launch your boat.