Squeal

[Ken Juul]

The last couple times we have had the boat out I am getting a high pitched squeal from the prop shaft.  Bottom and shaft was just repainted, cutlass bearing was replaced last summer.  Shaft packing is Gore dirpless about 2 years old, no debris in packing gland, runs cool.  Squeal only occurs in the 1100=1800 rpm range, doesn't change pitch with rpms.  An old Tech Note says it is probably paint on the shaft rubbing on the cutlass bearing, will rub away eventually.  Anybody else have this happen?  Other thoughts?

[kwaltersmi]

Check the tranny fluid, though you probably have already.  Any recent knicks/dings in a prop blade?

[Roc]

Had this happen...  what needed to be done is to have the prop re-conditioned.  I was told the blades had too much of a sharp edge.  Had the prop re-conditioned and the sound went away.  I've used Black Dog propeller with Prop-Scan technology....

[Ron Hill]

Ken : Try taking a file and flattening the leading & trailing edges of your prop blades!

A thought

[lazybone]

Ken : Try taking a file and flattening the leading edges of your prop blades!

A thought

Trailing edge needs to be very slightly squared off.  IIRC.

From the interweb...

Anti-singing Edge
The singing is a result of propeller diameter and R .P.M. , Boat speed and Trailing-edge thickness and shape or roundness. In most of the cases not much can be done on Diameter, Rpm's or speed, but we can modify the Edge Geometry. This has been the Strategy for all efforts to eliminate singing.
Most Propeller professionals (and others) are familiar with the Anti-singing Edge – a Chamfering of the Trailing edge, typically on the Suction side. This shape avoids the creation of curving flow eddies by cleanly separating the water flow off the blade.
The following graphic shows the Chamfering that goes from 0.5 or 0.4 Radius to the tip of Suction Side.



However the adoption of unduly thin edges can result in erosion or fracture of the blade near the edges. Anti-sing Edge may be considered as a last resort to minimize the Singing of an existing Propeller

[Noah]

Interesting phenomenon. Learn something new everyday here. If indeed this is  "prop singing", what has changed over time that would cause the edge of your prop to mysteriously get sharper, or react/sound differently than years past? Very odd hypothesis to wrap my head around.

[lazybone]

I would guess that a very tight packing gland which doesn't allow any water lubrication could also cause a harmonic squeal.

[Ken Juul]

The prop got a good wirebrushing and sanding before painting.  Nothing special done to the edges.  Going to have to wait for the water to warm up a bit before I attempt to square the edges.  Kind of hate to scrap off brand new paint

[Noah]

Painted your prop? With what? My general rule is never paint the underwater running gear. That may be contributing to your issue. Caveat: I have a diver "wipe down" my boat once a month ($40 per mo.).

[Roc]

I use Prop Coat Barnacle Barrier...

http://www.pettitpaint.com/product.asp?id=262

[Ron Hill]

Guys : You can also buy a spray can of "Rust-Oleum" zinc metallic paint for about $10 at Ace Hardware.

A thought

[Roc]

Hi Ron,
Does the Rust-Oleum paint work well for you?  do you use it by itselft, or do you use it as a basecoat and paint the prop and shaft with bottom paint on top of the zinc metallic paint?

[Steve McGill]

Works well on MY BOAT, third season. I normally dive on ours about 3 times during the April thru November season.
Always pleased on the condition of the shaft and prop.

Fortunately I have not experienced the squealing sound and any RPM

[Ken Juul]

I'm trying the pettit stuff this year.  In the past I have just used bottom paint or nothing.  Neither seems to work very well.  Neither caused any squealing.  I don't mind diving to scub the prop unless the stinging nettles (jellyfish) are in season.  Noah send your diver this way, locally it costs over $100 per event, little less if a monthly contract is signed.