StayCoolPumps Impeller Kit Replaces Westerbeke 34440 Sierra 23-3307 New Impeller Kit contains impeller, screws , and gasket. Replaces: Westerbeke 34440 , 034440 , Sierra 23-3307 Includes: Impeller , 2ea SS Screws , and Gasket. Fits pumps with the irregular cover made prior to March 2004. If your pump has a round cover it will not fit, use impeller kit 48500. Will NOT fit pumps that have a round cover and use an o-ring. The shaft size is different.