Abstract: Heat recovery apparatus for extracting heat from a hot flue gas stream especially useful on a marine vessel. The apparatus includes a housing having opposite outer end walls, opposite outer side walls, a top wall and a bottom wall with a heat exchanger extending between the end walls spaced downwardly below the top wall, above the bottom wall and inwardly of the outer side walls. An inlet chamber is formed in the housing having an inlet opening in one of the end walls above the heat exchanger for receiving the hot flue gas stream and the inlet chamber includes a downwardly sloping wall for directing the incoming hot flue gas stream to flow downwardly through the heat exchanger toward the bottom wall. A pair of inner side walls are provided on opposite sides of the heat exchanger spaced inwardly of the outer side walls for directing the hot flue gas stream downwardly through the heat exchanger to a low level above the bottom wall.