From the Citizen story:
Quote:
Verdonck explained that there are two types of exhaust systems: a through-hull and an above-hull system. Through-hull systems push the engine exhaust out through the propeller, which does not create much noise. Verdonck said many of the high-performance boats require the above-hull exhaust systems because of the increased pressure created by such boats. Because the above-hull systems are exposed out of the water, the sound must be controlled by a muffler.
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What about exhaust systems that are below waterline but
not through the propeller? Does Verdonck know there are more than
two?