Take good care of the cooling system - change to a new impeller every year. The impeller is very important. Its task is to pump water through the cooling system of the engine. Remember the impeller should be replaced every year and always make sure you get a Johnson original impeller, then you'll know it matches your pump exactly. Made of MC97 for cooling. Replaces Sherwood part number 1700K/Replaces Jabsco part number: 18958-0001/Engines/Pumps: Cummins 6B 300Hp B Series; Cummins C Series; CAT 3208; CAT 3116; CAT 3126; Deere 6076; Sherwood Pump P17 series.