Outboard motor exhaust system

An outboard motor comprising a lower unit including an outer housing and an inner exhaust housing mounted within the outer housing, the inner exhaust housing defining an exhaust chamber, the upper end of the inner exhaust housing having therein spaced first and second exhaust inlets, and the inner exhaust housing also including a first exhaust pipe having an upper end communicating with the first exhaust inlet and having a lower end communicating with the exhaust chamber, a second exhaust pipe having an upper end communicating with the second exhaust inlet and having a lower end communicating with the exhaust chamber, and a connecting exhaust pipe having opposite first and second ends respectively communicating with the first and second exhaust inlets, the connecting pipe being open only at the opposite ends, and a two-stroke internal combustion engine including first, second, third and fourth cylinders and first, second, third and fourth exhaust gas ducts having respective first ends communicating respectively with the first, second, third and fourth cylinders and having respective second ends, the second ends of the first and third ducts communicating with the first exhaust inlet, and the second ends of the second and fourth ducts communicating with the second exhaust inlet.