Disclosed herein is an outboard motor comprising a cylinder block including a lower horizontal drive shaft housing mounting surface, and a cylinder head mounting surface extending upwardly from the drive shaft housing mounting surface, a drive shaft housing including a peripheral outer surface including an upper end, a cylinder block mounting surface at the upper end, and a portion extending rearwardly from the cylinder block mounting surface and having therein a vertically open bore located forwardly of the outer surface, and a cylinder head comprising a cylinder block mounting surface fixed to the cylinder head mounting surface and including vertically spaced first and second recesses adapted to respectively form portions of first and second combustion chambers and respectively including first and second exhaust ports, a bottom surface extending transversely rearwardly from the cylinder block mounting surface of the cylinder head, a projection extending downwardly from the bottom surface and into the bore, and including an end surface having therein an exhaust gas outlet, and an internal exhaust passage extending between the exhaust ports and the exhaust gas outlet.