St. Clair Riverfest presented by McLaren Port Huron happens this weekend in downtown St. Clair and with it, the main event- the River Classic Offshore Powerboat Races are the biggest part of Riverfest and will take place on Sunday.  Boats are expected to run throughout the weekend as they familiarize themselves with the course, and do some fine tuning. The Powerboats race in different classes as part of the Great Lakes Silver Cup Series and the Offshore Super Series.  As anyone who has been down there in past years can tell you, those boats are a site and sound to behold. There will be hospitality tents, family friendly activities, and more. On Friday The Spin Doctors will perform and Blue Oyster Cult will perform on Saturday.  They are giving away complimentary VIP tickets to each of the shows, and the drawing ends on July 25th. To enter, head to the St. Clair Riverfest Facebook page.