Look for leaking tranny oil. The aluminum transmission case sometimes corrodes; holes develop. Normal for control cables to eventually rust, but these can be replaced without much trouble. This must be a Centri. Good machine. Corrosion attacks wiring at splices and various connections.
Check pump output. At full throttle, opinions vary, pump should put out about about 112 ounces per minute when both nozzles are combined. Ideally, spray pattern on concrete should be about 11 feet wide and fairly even. Electric pump can be replaced easily, but often the wiring is corroded and output can be improved with new wiring.