Please click here to view a FAQ addressing this subject. Should the fault isolation indicate a transducer failure, then the problem may be resolved by replacing the transducer with another compatible fishfinder transducer. However, should the fault isolation indicate a failure within the display, then the fishfinder would need to be replaced as Raymarine's Product Repair Center can no longer service DS400X/500X/600X Fishfinders. This class of fishfinder is typically replaced with a Dragonfly 4 Fishfinder or an a67 Multifunction Display.
Regarding Speed (through water) the fishfinder must be interfaced to a fishfinder transducer having a speed through water paddlewheel. Please respond with the model of transducer which has been interfaced to the DS400X.