strange noises mercury 9.9 4 stroke

[clar8]

Hi everyone, I wanted some advice from people more experienced than me about my Mercury 9.9m 4T of 2015. The engine gives me 2 problems:
1) When I accelerate, when the idle is exceeded, I hear a strange noise that vanishes if I continue to accelerate. The same thing happens when decelerating, just before reaching the idling speed you can hear the stridor that then vanishes at idle.
2) When I decelerate and go to idle, the engine runs erratically for a few seconds and then settles.
I enclose a video with an audio recording of the engine:
https://youtu.be/rMT75ak-Wj8
The spark plugs and the thermostat have just been changed.
I checked the valve clearance and it's ok. The belt is in good condition. For the irregular idle, I think it's the carburetor that I will clean. I have no idea what the other noise is.
Can anyone help me?
Many thanks in advance.

 

[fastjeff]

Sounds to me like something is vibrating at an engine speed that happens to be its natural frequency.

I suggest removing the cowling and grabbing anything that can "wiggle" while holding the motor at that speed.

Jeff

 

[eddie75]

Hello friends, I attach to this post becuase I have same noise on a brand new mercury 9.9 4 stroke. Dealer last year said noise would go away in time, but its still here. He put some grease on the long staff with gear that goes inside engine head. I am bored to be joked and to see my new engine dismounted so I asked for replacement under warranty (engine is 11 months old) and I'm gonna send everything to my lawyer here in italy.
Here you can hear the noise.
I think I readed somewhere that this noise is from oil pump or main bearings. Ofcourse I would never accept they open my engine head to fix it.
Any clue? https://www.youtube.com/watch?v=is-oD5HiYoM
thanks

 

[Bubbles1978]

I have the exact same noise coming from my brand new 9.9 mercury. Let me know what you guys find . TIA

 

[tom n]

I have the same issue on new 9.9 mercury (June 2024), howling coming out of idle then less, but still there at higher rpms. Did it right out of the box. Dealer and mercury are giving me the run around.

 

[tom n]

I also wanted to add it only does it in forward. Not in neutral or reverse.

 

[tom n]

I also wanted to add it only does it in forward. Not in neutral or reverse.

Problem solved. Dealership finally took it on the river and hear noise first hand. They replaced the original prop with a new one and sound went away, put original back on and sound was back. So they gave me the new prop and all is well. The techs said they examined the original prop and could not find any defects, but obvious something is wrong with it.