Couple of these pics are from the Saginaw Bay ( Lake Huron) but the one with all the boats is from Marble Lake near Cold Water, MI. It's a chain of lakes, but the main gathering is at Marble. There is a website for "Michigan Hot Boat" and they have an event schedule posted for the year. Gatherings at lakes all around Michigan every few weeks. Lots of grudge racing, and just motor talk to be had 