Mike,
Your Q may have become "overcome by events" by this time. If not I suggest you post the question to the Raymarine online customer support site. I post their URL next.
Raymarine Marine Electronics - Support Home
I have always had good response from them. Stick with them until you get closure, they don't mind repeated Q's, or follow-ons.
They should be able to provide you with the expected Voltage output to measure as you spin the paddle wheel, as well as most likely source of the problem. Generally these things fail somewhere in the cabling or connections. An inexpensive digital multimeter will help you test the voltage at the device and back at the display unit.
Best Regards,
Wayne