Abstract: A jet propulsion system for watercraft employs twin impellers contained within a common housing assembly. The housing assembly defines an intake duct that delivers water from a single water inlet opening to impellers supported within the housing. The inlet opining can be positioned centrally on the watercraft to avoid drawing air in during abrupt maneuvering. A dividing wall extends from a location forward of the impellers into the water inlet duct to divide the flow of water well upstream of the impellers. The dividing wall is configured to reduce cross-effects caused of the counter-rotating impellers in the water flow upstream of the impellers without requiring any substantial change in direction of the water flow from the water inlet opening to the impellers.