Sierras 18-3008 Impeller is designed for use with the following Mercury outboard engines: 10 HP (s/n 500022-1057993), 16 HP (s/n 700000 & Up), 20 HP (s/n 860970-1292909), 22 HP (s/n 1158546-1238089), 30 HP (s/n 950250-1260724), and 40 HP (s/n 941751-1224480). Includes one impeller per package. It is interchangeable with Mercury Marine 47-20813 and 47-25287. Each Sierra product meets or exceeds the original equipment part it replaces. Fit specific, check part numbers to ensure proper fit.