Sorry I'm not sure where the M'ville launch is but, If you take 94 to Port huron just before it ends is water street go right(south) on the left about a mile down, just past the rr trax(I think) is the PH municipal launch 6 bucks fill out envelope and go you can fish all the way down to marysville and the current will get you there pretty quick or just drive down, sorry I couldn't help.good luck.
Take 94 East to Marysville exit (Gratiot Ave). Go about 1 mile and in center of town, turn right on Huron st (Main street, center of town, stoplight - you can't miss it). Take Huron until it ends at river. Turn right and launch will be IMMEDIATELY on your left.