Blue to Shield should read anywhere between 2V and 5.8V DC. If the head is damaged, you may need to provide this power from another source to test the masthead. This is the masthead power supply, coming from the ST50/ST60 display head. Red to shield should read 8V DC steady. Test at the connections on the rear of the display head, or at the base of the mast (if you have a junction box installed), making sure that everything is connected and powered. With the multimeter, check the following: Normally the ST50/ST60/i60 display head would be energized and provide this 8V, however in your case, you may need to power the masthead transducer seperately. You will need to supply 8v to the masthead across the red and shield connections. To perform the check, you will need a multimeter, and a DC power supply. The currently manufactured masthead transducer (shown below) may be serviced with part number A28167: If cups are shaped hemispheres, then the part number for the service kit is A28167. If cups are shaped like trapezoids, then the part number for the service kit is E28081. Raymarine has produced two types of transducers for the ST60 Wind Instruments. Before performing the test below, the masthead transducer should be inspected to verify that its cups and/or vane has not been broken and that the transducer is securely tightened to the masthead block.

Raymarine st60 wind service manual