Where any county issues or has heretofore issued the bonds of the county under this chapter or any previous statutes of a similar character, an excise tax of not exceeding three cents per gallon, in addition to any such tax levied and collected by the state in such counties, for the distribution of gasoline, may be collected by such counties. Such collection shall be made at the time and in the manner provided for the collection of the gasoline tax generally and shall be remitted by the auditor of the county at the same time as is remitted the amount due to the county out of the regular gasoline tax. The additional funds so derived shall be applied first towards any deficiency in the amount collected by the state and paid to such county which may be necessary for the liquidation of the interest accruing on, and to provide a sinking fund for the retirement of, such bonds issued by municipalities for road protection and refunds as hereinbefore provided. Any overplus or parts thereof may be used in the construction of road protection pavements or hard surfaced aprons to any existing road protection heretofore constructed, or to increase the strength or stability of any such existing road protection, or in the construction of additional road protection, or in the repair and maintenance of existing road protection, or road protection hereafter constructed, as the board of supervisors may elect. The taxes hereinabove provided for, upon the faith of which bonds may be issued, shall be levied and collected annually in an amount estimated to be equal to the interest and sinking fund on said bonds and shall not, until said bonds with interest thereon shall have been paid, be lowered beyond that amount which is estimated to be necessary to produce annually a sum sufficient to pay interest and provide a sinking fund, requirements on such bond issue or issues, provided such tax shall not exceed such reasonable sum as may be legally levied and collected; said tax and sinking fund may be used by the board of supervisors to retire bonds issued by municipalities for road protection purposes and refunds as hereinbefore provided.

Any such county may exempt from the payment of the additional tax levied on the distribution of gasoline, any and all gasoline which may be consumed by boats engaged in fishing, by boats in commerce between the states or in necessary duties as instrumentalities of the United States government, gasoline purchased for agricultural purposes or domestic purposes, as was defined by Section 12, Chapter 264, Laws of 1946. Such exemption shall be contained in the order of such board of supervisors levying the tax on such gasoline and, when such exemption is granted in such order, then no additional tax shall be required from the person distributing gasoline direct to consumers using same in operating boats for fishing, in commerce, or as instrumentalities of the United States government. When a distributor is entitled to the said exemption, he shall, when reporting and remitting to the auditor for the regular gasoline tax, report also in detail with respect to the distributions exempted from said additional tax in the same manner as is required in the section on exemptions and allowances in the chapter on gasoline taxes.