Abstract: Two embodiments of improved exhaust gas systems for outboard motors. In each system, the slow speed exhaust gases go through at least three expansions and contractions before discharge to the atmosphere. In one embodiment of the invention, the slow speed exhaust gases go through four expansions and contractions. In each embodiment of the invention, one of the expansion chambers has communication with another expansion chamber through a neck that is tuned whereby the neck and the one expansion chamber function as a Helmholtz resonator for tuning intermediate and high speed exhaust gas discharge.