A molten metal pump includes an impeller disposed at the end of an elongate drive shaft. The drive shaft is disposed within an elongate, hollow post. The impeller and the end of the post are adapted to be immersed in molten metal. An inert gas is conveyed through the gap between the outer surface of the drive shaft and the inner surface of the post, which gas is discharged into the molten metal in the vicinity of the impeller. Because the drive shaft is insulated from the molten metal, it can be made of a durable material such as steel; because the post is stationary relative to the molten metal, the metal is stirred only by the impeller, and not by the drive shaft. The invention includes other features such as a quick disconnect capability and a radial adjustment capability.