Navionics may be your answer. They have an online chart viewer and an app for your smart phone. Rivers can change over time with silt/sand gravel bars changing the channel locations so I would not totally rely on a map that may be years old. Go slow in areas that you are not certain about and might be a good time to get a new depth finder. I wouldn't think the lower end of Elk would change much with silt but the area near Elk River Mills Rd may be subject to channel changes.

David