Well after Michigan EO 2020-42 and the updated FAQs as of 4/10, motorized boat activities are not included under outdoor activities until the end of April. Extracted from the link.
“ Physical outdoor activity like kayaking, canoeing, and sailing is permitted under the order, but using a motorboat, a jet ski, or other similar watercraft is not. Any outdoor activity permitted under the order, including boating, must be done in a manner consistent with social distancing, and individuals should use only their own equipment to prevent the transmission of the virus through the touching of shared surfaces”.
https://www.michigan.gov/coronavirus/0,9753,7-406-98178_98455-525278--,00.html