tHATS A RADAR DEFLECTOR
+1 to gkesden
Buy a wire tracer - absolutely invaluable on a used boat. My first one cost CAD120 some years ago. I just bought another for CAD28 on Canadian Amazon.
Nick F
That looks like a radar reflector. If so, it’s a horrible thing to have attached to an antenna! It will massively affect the antenna tuning.
Ken