I have an '06 Honda BF8 power thrust, power tilt that seems to run fine otherwise but it emits a high frequency whine or noise at just a certain rpm. My tach displays only the revs of the BF135 main engine so I don't know the exact rpm of when this sound manifests itself but it is above idle and below mid speed. In fact, it's at the rpm perfect for some kinds of salmon trolling so it's annoying to have to listen to.

The sound is almost like a ringing or squealing and disappears if rpms move above or below the affected rpm. The engine has had this noise since I bought it used 11 years ago. I changed the impeller two years ago and hoped that was the problem but alas, no.

Any ideas? I know it's sort of a long shot but you never know.

Thanks!