“Could be wiring – salt water/air brutal on harness, wiring, etc. – even when washed down properly. One way to check is to get a simple tester and ensure you are getting power to the thruster with switch on. If so, may be a thruster issue, if not, continue to trace wiring backwards to find where you are loosing voltage via corrosion or chaffed wires, etc. Just a thought and good luck! “