A25 singing propeller ?

[nebulatech]

I've never heard that kind of sound before on any diesel inboard I've operated, large or small. What my mind imagines when I hear that is the shaft is vibrating in the cutlass bearing. No idea if that's right or not, but it seems odd to me that you would hear a high pitch sound like that from the prop, coming through the water. But you're stating the experts all agree on prop squeal. They're probably right....

[honza]

Thanks. Plays well for me on my Mac. Nobody knows 100% what it is. The experts mostly think, that it is somebody else's problem. The prop is going to General Propeller, Brandenton, FL tomorrow. Joy said, that Pablo would do it at no charge, me just paying for the shipping. I still think, that it is the gears inside the box. We'll see.

Just, if anybody is wondering. The RPMs called out are the ones of the engine, the shaft runs 2.6 times slower.

[nebulatech]

Have you heard anything back from the prop shop, or otherwise any update on the singing prop phenomenon?

[Bob Noodat]

Whatever the cause(s), it sounds very much like a beat frequency, with two contributors. Especially on the second recording above.

To narrow the field a little, I'd be using my $9.99 mechanic's stethoscope with metal probe and moving it over all possible culprits,. Can't harm.

[DesertAlbin736]

We get similar noises from a band of about 1,100 engine RPM or so up to around 1,400. But after that it stops 'singing' and even when the 'singin' is going on there's no issue with a 'beat' component or excess vibration.

[RobS]

Too bad you need to pull it and ship it. I've seen this corrected with a short haul and just dressing the edge and then drop her back in. Hopefully it corrects your noise. Keep this updated and good pics of the prop edge geometry would be handy too.

[LopezMike]

Horrible racket. The only time I've heard this sort of commotion was when a shaft was touching another metal surface. I'm wondering if the shaft is making metal to metal contact where it passes through the packing gland. Or somewhere else.

I'm making the assumption that this only happens when in gear. In forward only?

[honza]

I was not getting updates on this thread, so i kind of forgot about it. The prop shop called, that the the no- sing edge was already machined on it at the prop factory (Michigan Wheel made somewhere in The Philippines?). Next week, hopefully, the dealer, I bought the Beta from, should be installing a new transmission. I'll keep you posted.

Yes, it is in fwd only and changes with load.