charts (those big paper things) and gps chart plotters have depth markings. I would not rely on either. They will help give you a general idea, but you are on the great lakes. Water depth fluctuates. Sand bars get bigger, smaller and move around. theres rockpiles, unknown/unmarked shallow spots. So there is nothing better than knowing the body of water your boating in.
There are several members in your neck of the woods, buy em some beer and take them for a few boat rides and have them teach you the lake. Beer and boat rides for local members that know they area will be cheaper in the long run then relying on out of date data while trashing props and outdrives.