When the first mixed flow jet was designed with the double row thrust bearing the largest engines coupled to jets was no larger than 327 cubic inches. Then as jets became more popular, they were coupled to “big block” engines in relatively light weight boats. Although they were big block engines, they could cruise around at three thousand RPM’s or less. Also very few engines could actually produce more than 500 “real” horsepower, so the load on the thrust bearing was relatively low. Today, boats have become larger, engines have grown bigger, and the little double row thrust bearing is not able to take the load.
American Turbine has again come up with a solution. We have incorporated the “QJ” style “true” thrust bearing into a kit for American Turbine, Dominator, Berkeley, and Legend jets. The “QJ” style bearing is a proven design used in our SD309 jets for seven years. This bearing package has proven itself on the rugged rivers of the Pacific Northwest as well as the 120-mph marathon race boats. The design of this bearing package also allows us to address another problem area “water penetration into the bearing cavity”. With the current design water can be sucked between the splines on the driveline and the mating splines on the pump shaft. Water in the thrust bearing is probably responsible for more than half the bearing failures. We have designed the bearing pre-load / seal ring to solve this problem. This device allows us to pre-load the inter race and provide sealing to the bearing housing independent of the driveline.
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