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.

[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.

I dug out the old flax packing. There were two pieces one was destroyed and in tatters. The other was in decent shape, but I think I over tightened the nut (by hand) and it caused it to vibrate when I am at low rpm going into gear. Trans is working well, and at speed I have no issues. I only had enough packing to put one ring on the shaft.
I ordered more flax today.
When I took the boat out to test all went well after one trip around the lake. When I idled back to the dock and put it into gear it made a very soft sound. Nothing like the scraping sound it did. I'll try and put the good piece back in, so I have two until my new flax arrives.

[Holdmybeer]

Good deal. Hopefully once you get it all together thr noise is gone.

Based on your declscription I never though engine trouble just something that rotates. Makes sense the packing was dragging on the shaft.

[SkiBoy]

A different noise now. Once I repacked the flax, doing all recommended procedures, we skied twice and no issues.
Sat on the water for a while and started it up to head to the dock. A tic tic tiika tic sound from the rear shaft - trans area. Fairly loud. I shut it down. Waited a few seconds and started it up. No more issues coming in. I changed the trans fluid yesterday (normal look, no burned smell) put it in gear- forward and reverse a few times, watched the shaft and heard no noise.
The noises always seem to happen after skiing when it's at temp and as it goes into gear. First the screech and now a sound like something is bouncing around.
Loose part? I can't find a similar sound online when Searching for Indmar engine/trans noise.
Could it be a damper plate issue?

Thanks

[Holdmybeer]

Did it make the noise on start up or when put into gear?

Transmission is not active when starting but the clutch plate does spin at startup. Worn out plate or loose bolts? Someone rattled lose and then it fell out after starting.

Are your prop shaft bearings tight? The bearings (brass sleeves) wear in the strut and will let the shaft bounce and rattle.

[SkiBoy]

After I warmed it up, we pulled out to ski and it made the kkkck sound in gear and out of gear.

It's hard to determine where the sound is coming from, but it only happens at low rpm. Lifted the cover and saw the belt jump a little when it screeched. Could be the new upper circulator I put in a few weeks back touching somewhere, or the belt is too tight, or too loose. Lubed the belt and it sounds good.
Will test it today. I will check the brass fittings as well.

[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.

[SkiBoy]

I tightened the belt and the noise almost is silent. I don't want to overtighten, but I may go a bit more.

[SkiBoy]

I have three ski runs since I got the new flax packing and tightened the V belt. Runs great no sounds coming from the circulator or shaft area.
I was worried I had the belt too tight, so I backed it off a bit a while back. I guess I had it too loose as it may have been slipping and affecting the circulator.

Anyway, all good for now.
Thanks for your input!

[Holdmybeer]

Good deal. Sorry.for not replying but you were making your way through the fix.

Rule of thumb, belt deflection should be no more than the width of the belt. So 1/2" wide belt is up 1/4" and down 1/4", anymore and it is too loose. Again, this is general not specific to your circulator.

[SkiBoy]

Thanks for your help on this. I missed a few runs and chased some sounds, but all is good for now. With a 27 year old boat, things go wrong and I hear 'sounds' now and then.

I will check the belt again and maybe tighten it a bit, and put that on my check list from now on.

Shorter season this year as the lake was lowered for dam repair and causeway reconstruction.

My boat is usually in by May 10th and out by the end of October, and I get around 120 runs in.
Could hit 60 this year due to chasing boat issues, and not getting it in until late June.


Thanks again!