Abstract: An enclosed shaft system for tunnel jet drive marine propulsion systems for providing an improved lubrication and coolant system over current designs. The preferred embodiment of the present invention contemplates the utilization of an enclosed shaft system wherein the drive propeller drives a portion of the water passing through the tunnel drive through a water intake, which water is filtered and directed to a "T" fitting, wherein a portion of the water is directed to the engine for cooling, and the remaining water is directed to the base of the shaft housing, wherein the water passes through an shaft sleeve enveloping the shaft, the shaft sleeve terminating at an open end wherein the cutlass bearing and propeller is fitted. The water passing through the shaft sleeve both lubricates the cutlass bearings, as well as cooling same.