Exhaust system for a marine propulsion device having two stationary tubes to define an annular exhaust passage

摘要

A marine propulsion system is provided with inner and outer bellows, or tubes, which are rigidly attached to both the transom bracket and the driveshaft housing of the sterndrive system. Neither the inner nor outer tubes rotate with the driveshaft. Both the inner and outer tubes, or bellows, allow the driveshaft to rotate relative to the transom bracket about either a steering axis or trim axis. An exhaust passage is defined between the outer surface of the inner tube and the inner surface of the outer tube. This structure provides an efficient positioning of the two tubes while protecting the universal joint within the inner tube from the exhaust gases. Encompassing the inner tube within the outer tube increases the possible area that can be used for the exhaust passage in comparison to providing two individual tubes, one for the universal joint and the other as an exhaust passage.