Whistling sound at higher rmp

[Titomania_79]

Hi,

I have Yamaha f60 from 2012. Lower units was stolen and replaced. After that, I noticed that it started to make “whistling” sound at 3700-3900rmp. If you increase the speed it disappeared and the same thing below 3700.

Does anyone have any idea what it could be?

[99yam40]

maybe the drive shaft bushing needs some grease