As recommended above first check the fuses. I have had one fail such that it had a break which was not obvious until it was removed. After doing this obvious check call Ranger as they probably get more calls about this than anything else and can probably walk you through the checks over the phone if they are not busy. The Imra manual has pretty thorough trouble shooting information as well, (are they still Imra?) This can be downloaded from their website. While you are at it check the flow on the weep holes to help keep water out of the rear thruster compartment. There is also lots of history on this forum about thruster fixes and frustrations. Hope it is something simple.