I have a one hp AO Smith electric pump motor for my sprinkler system which is approximately 5 years old. Well point is clean and all sprinkler heads have been replaced. I am not able to get distance from my sprinklers into the lawn. Could this be due to a worn impeller?

I don't understand why it would drop after a few months. The impellar probably did not wear. It is more likely that the water level has dropped in the well, but this is unusual, too. If these heads rotate, they work best at around 50 psi at the head. There are small losses through the main piping, control valves and piping to the heads. If you can lower nozzle sizes on the heads to get around 50 - 55 psi at the pump, distance will increase. Try one zone and see the result.
Gary I don't understand why it would drop after a few months. The impellar probably did not wear. It is more likely that the water level has dropped in the well, but this is unusual, too. If these heads rotate, they work best at around 50 psi at the head. There are small losses through the main piping, control valves and piping to the heads. If you can lower nozzle sizes on the heads to get around 50 - 55 psi at the pump, distance will increase. Try one zone and see the result. Gary