The thruster only works is you are going very slow, or when you are not in motion at all.
Perhaps you are sailing too fast to make the proper turns, so I'd suggest slowing down, and thinking much further ahead (with an eye on the radar/map aswell)
Taking it slower, planning turns (judging traffic etc) and using all the controls at your disposal the way they are meant to be used, will work!
Regards,
FRed