Intermittent scraping noise coming from engine

[SkiBoy]

Skied behind it this morning. The sound is coming from the circulator. Not as loud as yesterday and the boat runs like new. Smooth acceleration and no noise until rpms get low then the kkkck sound like a scrap every now and then. No sound when rpms are up. Only at idle and in gear or out. We watched the shaft putting it into and out of gear. No slop or vibration.

[SkiBoy]

Checked all brass on shaft. All tight under and above, no slop. Watched it run in and out of gear, no unusual sound or movement. I have always changed the fluid yearly.

All this started after I put in the replacement circulator. I may have picked up a piece of debris and it bounced around the aluminum backing of the circulator. (tough to pinpoint sound direction with the cowling on) Now I hear a tiny bit of scraping like maybe I mounted the circulator wrong or got a bad part. Like I said, once rpm are above idle no sound and runs great.

I'm baffled.