Grinding/Whining noise in neutral?

[natrix19]

2012 Mercury Pro XS 225
s/n: 1b863739

My motor is starting to make a sort of grinding/whining noise in neutral. "Grind" seems like strong word for the sound, but it sounds like a pulley scraping or something.

When I put it in gear (forward or reverse) it stops. Put it back in neutral and it will do it again.

It doesn't do it all the time, but something that seems to be happening somewhat frequently.

Any thoughts on what might be the culprit?

Thanks,
Nate

[EuropeanAM]

Have you removed the cowling and the flywheel cover for a visual inspection of the cover, belt, pulleys, etc? That would be a good starting point.

[natrix19]

Yep. I pulled the cowling and flywheel cover. The belt looks fine, no wear that i could see, no cracking or rotting, nothing. Pulleys looked fine too. There's some rust on the starter head, with some "clean" areas, which I'm assuming is just from engaging to start the motor. The belt and compressor was replaced a year or two ago, so they should be in good shape.

I ran it for a bit on the hose and it didn't make the noise. Like I mentioned, it seems to happen randomly, but with some frequency. As I said, it only happens in neutral. If i put it in gear, it stops. Put it back in neutral and it makes the noise again.

I attached a few photos to show the condition of the belt and pulleys.

It started happening mid-week last week while I was in Canada. It happened maybe 2-3 times per day. Then it was a dice roll if it would happen again the next time I started it. Performance-wise, I was having trouble getting above 5400 RPM, but that could just be related to the extra weight I had and how I had it distributed...tho I did recently get my prop fixed from some damage and had an ignition coil replaced... So I doubt this noise is related to my low RPMs

I was planning on taking it out Saturday with a lighter load to see if I can hit my normal RPM range at WOT. If it makes that noise again, I'll pull the cowling off and see if I can isolate the sound. Or do you think she needs to go straight to the shop?

PXL_20220621_171639909.jpg
PXL_20220621_171626638.jpg
PXL_20220621_171636994.jpg
PXL_20220621_171915971.MP.jpg

[EuropeanAM]

Unusual to have it only present in "Neutral"- the only moving objects that change are the propshaft, bearings, clutch dog and prop. Make sure you've checked the gear lube, just to be safe.

Might also put a torque wrench ("inch" lbs) on the Belt tensioner. Set the wrench to 70 lbs/in, and make sure it "clicks" before the tensioner reaches the end of it's travel. If not, the spring is weak.

Other than that... this will probably require hands-ears-and-eyes-on inspection.

[natrix19]

I'll check the gear lube. I changed it in April, but doesn't hurt the check.

I'll have to see if I have a torque wrench that does lbs/in

Out of curiosity, what bearing might it be? I think it's fair to say the sound it's making could be a bearing. And if it changes under load, makes me more suspicious lol

[EuropeanAM]

Technically "any" bearing.