Clean out the water passages as best as you can, and especially in the pressure relief valve area of the power head. Sand or mud in there will not let that part of the system function properly. New water pump is in order and remove the water intake screens (and clean them) looking for any mud that may restrict water flow behind the screens.

Just to be safe, check your prop thoroughly for any tiny cracks. Over time, tiny ones get big and then the blade slings. And stay away from sand bars!