The Handbook of Missouri Boating Laws and Responsibilities
The Official Boating Handbook of the Missouri State Highway Patrol, Water Patrol Division - Web Version
Table of Contents
A motorboat’s engine must have a factory-installed muffler or exhaust water manifold for noise reduction or another effective muffling system.
Motorboats built on January 1, 1996, or later must not exceed a noise level of 90 dBA when stationary at idle and measured from a distance of 3 feet.
All motorboats must not exceed a noise level of 86 dBA when measured from a distance of 50 feet.
You may not remove or modify a muffler or muffling system if the result is increased noise level.
If the exhaust system uses water for muffling, it must comply with the noise level restrictions.