Need help to increase the borewell yield


We had drilled a 6" borewell in January 2013 around 250 feet deep. There was a lot of water flowing outside during the drilling. Recently (August 2013) we installed a submersible pump of 2HP 20 Stage.

On swithing the pump on, there will be water for 2-3 minutes only. Initially for about a minute I get clear water later for 30 sec I get muddy water and then clear water. The water level in the bore is at around 20 ft from the tip of the bore, slotted pipe is installed for the full length of bore

Can anyone let me know what should be done to increse the yeild?