Unfortunately, there seems to be some confusion regarding the location of the boat ramp named Silver Lake. The coordinates provided in the question (latitude: 45.40955353, longitude: -89.62754059) appear to be for a location in Wisconsin, not Illinois.

Without knowing the exact location of the Silver Lake boat ramp in question, it is difficult to provide specific information about its characteristics, such as its width and the types of watercraft it allows. However, in general, boat ramps can vary widely in their size and facilities. Some may be only wide enough for one or two boats to launch at a time, while others may be large enough to accommodate multiple boats simultaneously.

As for the body of water that the Silver Lake boat ramp services, it would depend on which Silver Lake is being referred to. There are many lakes across the United States with the name Silver Lake. Some are quite small and may not allow motorized watercraft at all, while others are large enough for boating, fishing, and other water activities.

In order to obtain accurate information about the Silver Lake boat ramp, it would be best to consult local sources such as a state park or recreation department, or to visit the location in person.