2014 210 Mercruiser Engine "hum" or "whirl"

[hilsquad]

Brand new to the board but think I successfully searched and found no results.
We recently purchased a 2014 210 with the Mercruiser 5.0L with about 440 hours. Boat is super clean and performs great. When we took it out for the test spin, I noticed what can be described as a hum or a whirl. It's not a click or metallic in anyway and seems to either go away or at least disappear under engine noise when rpm's increase. Previous owner said it's always had it. I have some ideas but wanted to run by this group first. I've posted a link to a video with sound, the hum in the video is probably a little bit more high-pitched than in person.

https://youtube.com/shorts/IY5Ya1Z1eXY

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[AsLan7]

So glad you found us hsq.

That's your stealth whipple supercharger whine.

Honestly it could be a number of things but tough to diagnose from the internet. You may have a bad bearing, loose pulley or loose serpentine belt near the front of the engine. Like you mentioned, the water pump bearing, alternator bearing, and/or others can click, squeak or even whine depending on the severity of bearing damage. Also could be the air making noise thru the flame arrestor depending on any modifications. Hose suction leak. Or maybe you just keep leaning on that trim switch.

Others will chime in shortly.

Post a boat pic when you get a chance too.

And welcome aboard mate!

[Big Block Power]

So glad you found us hsq.

That's your stealth whipple supercharger whine.

Honestly it could be a number of things but tough to diagnose from the internet. You may have a bad bearing, loose pulley or loose serpentine belt near the front of the engine. Like you mentioned, the water pump bearing, alternator bearing, and/or others can click, squeak or even whine depending on the severity of bearing damage. Also could be the air making noise thru the flame arrestor depending on any modifications. Hose suction leak. Or maybe you just keep leaning on that trim switch.

Others will chime in shortly.

Post a boat pic when you get a chance too.

And welcome aboard mate!

Agreed.
But also add the fuel pump screaming at you. Take a long screwdriver or stethoscope to everything and move it around till you pin point it.