I washed the motor and the speedo stoped working

'Can't really say why, si nce most if not all cars no longer use speedo cables but an electronic sensor which is usually located either in the transmission, looks like a cooling sensor, or picks up the rotation on the driveshaft. Could be the wire going to the transmission somehow got detached, or the sensor damaged by the water. Check your fuse box and the box under the hood and see if a fuse blew.