The exhaust of every internal combustion engine used on any motorboat shall be effectively muffled by equipment so constructed and used as to muffle the noise of the exhaust in a reasonable manner. The use of cutouts is prohibited, except for motorboats competing in a regatta or boat race approved as provided in section twenty of this article, and for such motorboats while on trial runs during a period not to exceed seventy-two hours immediately preceding such regatta or race, and for such motorboats while competing in official trials for speed records during a period not to exceed seventy-two hours immediately following such regatta or race.