McMahon has been President of Pinnacle Marine Corporation (www.pinnaclemarine.com) since 1994, Pinnacle Marine is the largest broker of passenger vessels and passenger vessel businesses in North America. Pinnacle Marine provides brokerage of vessels, businesses and consulting to the industry such as the National Park Service.
McMahon was with Skipperliner Industries, Inc., from 1984 to 1994 departing as Senior Vice President.
McMahon is currently President & Chairman of the Board of Trustees of the Passenger Vessel Foundation, member of the Board of Directors of the Passenger Vessel Association (PVA), Associate Member Representative, he serves on the Finance & Site Selection Committees and as Chair of the PVA Associate Council. McMahon is a past Chairman of the PVA
He has served as; President of the Boys and Girls Clubs of Greater LaCrosse, a founding Board member of the Amie L. Mathy Center for Recreation and Education, a founding Board member of Tri Quest Charities’, Inc. and member of the Board of Education of the School District of LaCrosse, WI.