I'd call one of the major marinas in Port Clinton or that area and ask them. Try Drawbridge Marina in Port Clinton. They will know where big boats typically go if they want to launch at a ramp. Or they may be able to give you the number of a marine transport company that works that area - they would know.

There are some photos of the Catawba ramp at the website below, launch ramps page. 6-8 years old, but the basic ramp area hasn't changed.

Lake Erie Fishing Boating Vacation Recreation Information