The board of county commissioners of any county in this state having more than two hundred fifty (250) miles of lake shore line within such county, are hereby authorized to purchase, maintain, and to provide for the operation of, for the official business of the county and its several offices, a boat and motive power therefor, either inboard or outboard. No mileage shall be charged to the county for travel in such boat and all mileage collected by any officer, from any other source, shall be paid by him into the county and shall be credited to the fund from which claims for the operation of such boat shall be paid. The board shall establish such rules and regulations regarding the use of such boat as to prevent its use for other than official business.