I have a 2019 Merc 60 40 jet and it’s done this from day one at idle. It is the impeller rubbing the wear ring.
I don’t want to have to get over the noise on a new set up with 14 hours.
You can see wear on the ring the lower left 1/3 the rest looks new. I’m taking it back and expecting them to fix it.
This should not happen period especially on a factory set up. Very unhappy with it.