Mich. Comp. Laws § 324.45706
Any person to whom a license has been issued under this part may operate not more than 1 boat, with or without a motor, in taking, catching, or killing mussels. The person may use 1 additional boat, with or without a motor, for the purpose of towing only when an apparatus for taking, catching, or killing mussels is not used or kept on the boat. A person engaged in taking, catching, or killing mussels on the waters shall not possess more than 4 crowfoot bars, shall have not more than 2 of the bars in the water at 1 time, and shall not use or possess a crowfoot bar of greater than 20 feet in length. A person may also use his or her hands or a device known as a hand rod in taking, catching, or removing mussels from the waters. However, a person shall not use to gather mussels a fork, dredge, tongs, or other device that when used digs deeply into the bed of the stream. All boats propelled by an internal combustion engine or motor and used in taking, catching, killing, or conveying mussels taken under this part shall be equipped at all times with a quiet muffler for the exhaust.
MCL 324.45706