Silt collection near borewell motor pump

The borewell in our house is 4 years old. From a few months since there were no rains in Bengaluru we had not used the borewell. Recently, when the borewell was turned on, there was a burning smell . When checked with the plumber, he said that the silt/mud from the water has all settled up near the motor which is not allowing to pump the water up. He also suggested to remove the silt, check the motor and fix it back. He said the charges for all this would be around Rs.15,000. Is this a genuine case of silt collecting near the motor? What can be done to fix this? Please suggest.