One of the weak points in the 998 engine is the stock water pump impeller and shaft. The stock impeller is plastic. During normal driving, the plastic water pump impeller can actually separate from the impeller shaft which ceases the flow of coolant throughout the engine (The stock impeller is driven by a pin that will actually break the notch in the plastic impeller). If not caught quickly, this can cause a major failure in the engine.
The solution to this problem is this billet water pump impeller and precision ground 416 stainless steel water pump impeller shaft. Once installed, you will no longer have to worry about the plastic impeller failing and causing potentially thousands of dollars worth of damage to your engine. The new impeller threads onto its stainless shaft – unlike the stock impeller set-up which uses a pin to drive the impeller.