OMC Circulating Water Pump - 18-3578 OMC Circulating Water Pump - 18-3578 by Sierra. Please use the Red PARTS CHARTS button (top of any page) to locate the correct part for your application. $ 172.17               More Information      Quantity:     Circulating Water Pump - 18-3578 Circulating Water Pump - 18-3578. Please use the Red PARTS CHARTS button (top of any page) to locate the correct part for your application. All prices are per unit (50' Coil=50 Units, 2 PK=2 Units, and etc.). Verify your quantity is correct at Check-t and adjust as necessary. Send us an email (Contact Us button at top of any page) if you have any questions. $ 172.17               More Information      Quantity: