A vessel propelled by an internal combustion engine shall, when in operation, be equipped with an efficient muffler, underwater exhaust, or other modern device in good working order and in constant operation capable of adequately muffling the sound of the exhaust of the engine. An engine is considered adequately muffled when the motor's exhaust at all times is muffled or suppressed so as to not create excessive or unusual noise. The discharge of cooling water through the exhaust of an inboard engine shall be considered an adequate muffling device. The use of cutouts, or open exhaust stacks is prohibited, except:
Haw. Code R. § 13-243-4