There's always some confusion. Even the sheriff deputies change their interpretation sometimes on the more obscure ones (they found out a few years ago they were enforcing the old ordinances incorrectly).
The main ones they patrol and where you will have to no-wake it - minimal wake, but you can usually go above idle speed since the river is big and busy:
Starting at Riverside park - there's a no-wake marker in the channel just upstream from the boat ramp (east). The no-wake extends from the east downstream past the marina on the left and the island on the right. There is normally another marker in the channel there.
Next - Grand Valley marina/MDNR ramp - starting at the power lines (there should be another marker in the river) at the upstream/east end, a long no-wake downstream past the last houses - there should be another marker in the channel.
Finally - the loonnngg one from the sewage treatment plant (large pole markers at the channel edge with no wake signs on them way before spring lake a little ways past the downstream end of Indian cut) all the way to the mouth of Lake Michigan, and out into Spring Lake way out to the opening of James Bayou - again buoy markers and a large sign on shore.
Some guys take a shortcut through a northern channel off the main channel near Spring Lake and the village boat ramp, but their are definite no wake pole markers there too, so they are breaking the law. Also, many guys take the old South Channel behind Grand Isle Marina because they run a couple stretches so it is a little faster than following the main channel. I have done this, but near as I can figure, it may all be no wake even though it isn't marked so do that at your own risk. Guys have been doing it for years.
If you go the South channel way, you can make the lake in about 50 minutes to an hour at a minimal plow (800 - 900 rpms, some guys go much faster - that is their business). You should be able to see which part guys are running. They have not been marked in the past, but I haven't taken the shortcut in a few seasons, so watch yourself. Also, when you go through the old wooden bridge, only two openings are really open - in the middle - marked with small reflectors (I learned that one the hard way).
Now, supposedly, the whole channel from the mouth of Stearns down past Pottawattomee to the power lines near the downstream end of the Indian channel is also no wake. Most guys just run the Indian Channel anyway (unless they are going to Stearns). I have had some deputies tell me the whole channel is no wake and some tell me it is only the standard 100 feet from shore, docks, swimmers and anchored boats/floats. I don't run on plane past Stearns. Most guys run on plane into Stearns, but the legality of that is really iffy. On rivers, the 100 foot rule doesn't always apply in Michigan because of the wording of State law. But there are docks, and may be boats and even swimmers and it isn't very wide. I do not know what would happen if you run past a deputy. Again, there are multiple interpretations often. I imagine if you blow by boats no-waking it and/or close to dock ends and/or swimmers, and a deputy sees you, you may be in for a talking to.
As far as I know, all the other no wakes in the river channels are 'privately' marked or misleading because they are only restating the 100 foot rule. But again, my interpretations do not supercede regulations or the deputies, and things can change so be alert for markers in the channels, and signs on any of the channel markers - only government officials can put signs on the channel markers. Anyone can throw one in their yard and there has been a huge A-frame one at time upstream of Bruces that is not legal (just the 100 foot part) - if it is still there.
For the bayous, watch for the buoys in the water and bridges. Remember the 100 foot rule will apply in most of the bayous -they are treated more like lakes. Stearns has a no wake at the bridge. Millhouse has a no-wake going in through the mouth in the narrow part. Pottawat... does too at the mouth/bridge. Lloyds has a no wake at the bridge (you run that and you may end up sushi, plus there are stumps in the bay out in front and a real hair-raising run through to the small cut off the river that leads into the bay - wood all over the flat).
Part of the Lost Channel at both ends are no wake. There should be signs and buoys in various places.
In Spring, you have the big no wake out several hundred yards marked by buoys. All of Pettys is no wake (it is big, but...) and I see dingleberries running around back in there all the time even though the signs across the bridge clearly say no wake in the entire bay. There are buoy markers out near the main lake marking where the no wake begins. Part of James Bayou is no wake - the bridge area again into the bayou a ways. I keep expecting this one to become all no wake.
Almost all the other side bayous off the main Spring Lake are no wake. Most of the bigger ones have no wake bouys. Plus the north end of Spring is all no wake. Buoys again mark the start of that.
Are you confused yet? I probably have forgotten something. Mainly, follow the 100 foot rule, watch for buoys in the river/bayous, and signs on the channel markers. Those are all legal ordinance-based. Spring Lake is 200 foot rule too, not 100, due to heavy traffic.
The weird part is the actual ordinances were written to protect Indian Channel (major wetlands/marsh) and leave the main channel past Stearns open, but probably because there are houses along the main channel and none in Indian channel, the sheriff has been enforcing it the opposite way so long that when the reread the ordinances, they decided to keep enforcing it the way they had to not cause more confusion than there already is.
Sometimes there are no wake signs near the Indian Channel DNR ramp and back upstream a ways, but to my knowledge, these have all pretty much been put out by property owners and can only be enforced under the 100 foot rule. Again, my statements do not override ordinance, regulation and deputies with guns AND see my update based on their new online map at the end.
Watch for fog in the morning on the main river and the little walleye boats that love to drift all the way across the main channel back upstream from the Indian Channel to Bruces. Sometimes they are packed in there and guys run full out right through them. Very dangerous for everyone. Also, sometimes unwise people anchor in the middle of the Indian channel at the mouths and near the major wood. I've seen guys run all out within 10 feet of them. Crazy, illegal, dangerous. It is pretty dumb to anchor where they do, but that does not mean we can blow by them like they are a tree or something.
It gets a little hairy on the bends, in the fog and in the packs at the beginning and ends of no wakes. I try to get to the sides and let the mouth-frothers and bug-eyed have their way clear from me.
I'd suggest you call the Ottawa County Sheriff's office: Phone: (616) 738-4000 when in doubt, or email the marine Sgt Koeman: kkoeman@co.ottawa.mi.us
Remember our tournament weekend is also the Coast Guard Festival, so expect at least later in the day, that they will heavy traffic out near Lake Michigan with heavily patrolled marked lanes along with a more strict no wake coming in. Allow an extra 15 or 20 minutes for the activities and extra restrictions.
The Ottawa County Sheriff does put out a fairly nice brochure that covers Grand River regs and no wakes fairly well including a map if you can find one in the area. I don't think it is available online. (Well they have a GIS service, but it didn't work for me - well I got it to work the 2nd time I tried
http://www.gis.co.ottawa.mi.us/ottawa/waterrec.asp).
This map shows the no wake at Stearns back upstream and only a short ways into Stearns. It also shows a no wake for 3,500 feet just upstream from the mouth of Indian channel back half way to Bruces. It shows an open line right down the middle though - I have no idea what that means? They also show the main channel Stearns no wake ending at the mouth to Pott, but I've been told that version and the one where it goes to the power lines near Indian Cut.