On the last day of a four day trip, my boat's steering began to rattle, almost pinging when I turned the steering wheel. When I went straight, the pinging ended. I had been running fine for four days, then as I came into the no wake zone in the marina, it started. I smelled burning rubber for a moment, but it went away. The pinging continued as I pulled into my slip, but stopped at idle. My gauges were all normal. I didn't see any prop damage when I trimmed up the drive. What gives?