Intermittent scraping noise coming from engine

[SkiBoy]

Sometimes happens in gear, sometimes at idle. Not every time I operate the boat.
Boat is running fine not over heating.
It's a short kkkkch and then nothing. I rev the engine and all is good, or just keep it at idle speed.

Some days no sound at all.
Any ideas?

I have checked oil level and trans fluid, all good.

Thanks

[Holdmybeer]

If it is random and happens at any engine condition, then most likely not engine related.

When did you last replace your raw water impeller? Hard spots cause noise.
Hard spot is belt.
Idler pulley bearing.
Shaft packing seal needs replaced or adjusted.

[SkiBoy]

I check the impeller a few times a year. All the 'fingers' are there and it seems to be pumping well. Temp stays around 160. Packing seal I adjusted twice this year. I have a new piece, will put that in if I can dig the old one ones out. I did two pieces last time instead of one. Boat is in the water as my lake is down 10 feet for dam repairs, so no hoist this season. Could be idler pulley bearing. I hear a faint rattle and then a kkkkk screech when it sounds off. Once we're up to ski speed or higher rpm it hasn't happened.
Will report back. Thanks for the info!

[SkiBoy]

Checked the shaft packing, all good. I recall in the past overtightening the nut and it zinged on the shaft. I only hand tighten now to a slow drip every several seconds or so. That is not the sound I'm hearing. Started the boat today and ran it for a few minutes at varying rpm and no scraping noise. It's a quick loud kkkuuhkk sound. I am going to try and record it today and somehow post it so someone can hear it to try and help figure this out.
I don't see an Idler Pulley on my engine. It's a 5.7 with a simple belt. Water circulator, Alternator and main engine. Not a serpentine.

[SkiBoy]

I had a guy in the boat tonight recording sound. When I shift from neutral it makes a sound. He said it’s coming from the back and thinks it’s the shaft. Sound is not as loud as the last few days. I am changing the packing tomorrow. Will report back.
Pretty sure we have it figured out.