Best Seller | Sierra 18-3446 Water Pump Kit - Mercury 46-70941A3 The Sierra 18-3446 Water Pump Kit is interchangeable with the following: Mercury 46-70941A3. Each Sierra product meets or exceeds the original equipment part it replaces. Fits: 45/4.5 hp and 4 hp 1 cylinder O/B s with a .456 I.D. water impeller. more | | $66.49 FREE shipping go to store |