A worn or damaged impeller can cause system failure or engine breakdown. SPX FLOW's Johnson Pump Marine brand impellers are developed and manufactured for maximum flow and long life. With a genuine spare impeller you can also be sure that you are getting the quality required by engine manufacturers and professionals.• Compatibility: F4 Pumps• Quantity: Single• Excellent Self-Priming Capability• Ensures Sufficient Cooling Directly At Start Up• Optimized To Provide Maximum Life, Especially For Applications Where The End User Doesnt Run The Engine On A Regular Basis Ensures Correct Cooling Flow Stable Pressure Delivery Over Time Significantly Longer Service Life | Johnson Pump Water Pump Impeller, For Use With F4 Pumps