Too much sandy water in borewell

Borewell is drilled till 280ft. Got water at 90ft, however, after 110 ft got sand up to 160ft after that there is rock. Casing is up to 119ft. Now the motor pump is at 150ft. Getting to much sandy water. After few hours water is not coming, but the motor continues to run. This is happening again and again. What is the solution?