| 摘要 |
A number of embodiments of exhaust systems for marine watercraft, particularly, those of the jet propelled type. The exhaust systems all include an exhaust pipe which terminates in a discharge opening formed in a lower surface of the hull for discharging exhaust gases through the body of water in which the watercraft is operating. In addition, the exhaust pipe has an ascending and descending section with an expansion chamber communicating with the upper portion thereof through an opening so as to accumulate water if the watercraft becomes inverted and to direct the accumulated water back to the exhaust outlet opening when righted so as to preclude water from flowing to the exhaust ports of the engine. The expansion chamber also acts as a silencing device and may comprise a portion of a Helmholtz resonator. Furthermore, a low speed exhaust gas discharge extends from the highest portion of the exhaust pipe to the tunnel in which the jet propulsion unit is contained above the water level therein so as to provide a low speed exhaust gas discharge for discharging exhaust gases when the watercraft is operating at idle or low speeds. Various embodiments show different numbers of Helmholtz resonators and arrangements wherein the low speed exhaust gas discharge communicates with at least one of the Helmholtz resonators.
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