Congratulations on your new boat Graham, Your Maramu bow thruster may not be faulty. A couple of times when backing into a dock, I thought mine wasn't working but it was a really strong cross current. The size of the prop compared to the boat weight and movement sometimes delays the desired result.
Also I was told to only turn on for 10 seconds and then off for 5 seconds because it is not a constant duty motor, maybe some other owners with more experience could add their comments about this.
Happy New Year to All,
Ross in NYC, US
Maramu 1989 #261