Lakes in Southern Michigan
 

Are there any lakes in the southern half of Michigan big enough to run a 34' Offshore Boat ?

Since you're not specific on what side of Michigan, I would say Lake Michigan, Lake Erie and Lake St. Clair. All of which are in the southern half of Michigan.

Google Earth might be a good help for you. There are some good sized lakes, but some won't have a launch that can handle a 34' PQ, and then are the speed limits. Lake Michigan would be a better bet.

The area of Lake St. Clair offers many options. There are marinas, restaurants, bars, anchoring hangout spots, and numerous launches. It's also easy access to the St. Clair River or Detroit River for added activities.

Most "inland" lakes are no bigger than Cedar Lake (grew up in Highland)...the lakes or rivers along the west shore with channels to lake Michigan are more safe harbors for running in the big lake. You can access Spring lake at Grand Haven, but it is "no wake" for boats over 26'. You can run in Muskegon Lake, White Lake, Pentwater Lake, Pere Marquette Lake at Ludington, all with channels out to Lk MI. For inland lakes, there is Hardy Dam Pond at Newago,
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https://images.search.yahoo.com/sear...kend+Hardy+Dam

Or Hamlin Lake just north of Ludington, it has no access to Lk MI, but it is 12 miles long and dunes along the state park for hanging out.
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All inland lakes in Michigan have a 55 mph speed limit.