Prop Whistle?

[firstbase]

Pulled my PO four blade props removed due to bent blades causing vibrations. Had the original 3 blades tuned, balanced, and Speedpropped and then put back on the shafts last week. Vibration problem gone and can now get full RPM's on my FL SP135's. After cruising for an hour or so I have to pull back to 1000 rpms and noticed what I can best describe as a "whistle" coming from the starboard prop. Noise seemed to be exterior not in the engine room. This side had the most damaged prop with all four blades dinged/edge bends (port prop only had one blade with some end damage). Anyway, the whistle occurs between 1000-1200 RPMS. Fast or slower it goes away. Any hints from you experts (why do I already know this is going down the cutlass bearing road???!!! Anything else cause that type of thing? Diver who put them on said that it was an uneventful switch of props...

 

[Capt.Bill11]

In many cases the noise is coming from the strut bearing not the prop itself.

 

[meridian]

Prop "singing" comes from vibration of the prop edges. Sometimes a swipe with a file will cure it. It did for me.

 

[Gbinterim]

Props

Had the same thing happen to me. Refurbished an existing prop, no vibration but singing did occur. Took the prop off and sent it back to the prop shop, they detuned the edges. Ben happy as a clam ever since.

 

[Ski in NC]

When my prop sings, I know it is clean. A little growth, singing stops. I like hearing it.

 

[firstbase]

Ah, so the world (as I know it) isn't ending then maybe? That's good news! I will let it go a little while and see if a little South Florida growth occurs and knocks it down an octave or two.... Just wanted to make sure that the prop, strut and the shaft weren't about to fall off!

 

[Ski in NC]

With engines off, rotate prop shafts by hand. If shaft is easy to spin, nothing will be rubbing hard enough to squeak, then most likely prop singing. Redneck shaft alignment check.

 

[markpierce]

Propeller removed second time until the shop removed the singing.

 

[Hawkeye]

Recently had a bent blade repaired on a 4-bladed prop and reinstalled it. Prop "sing" at 700-1100 RPM which lasted a few engine hours then disappered. I googled "prop sing" and learned a lot. A harmonic sound can occur with a prop whose blades "are too perfect" as in perfectly tuned to original spec. Sounds weird but mine went away. Others wait for a barnecle to ahere or a ding.

 

[Knot Salted]

I think we just experience 'singing props'.
First time out this season, pulling back from 2000 to 1200. Very noticable humm. Very repeatable many times. Had installed shaft zincs (magnesiums) for first time ever on the boat -far as I can tell.
We thought one might have slid back to the cutless. 44 degree water was not welcoming an inspection, and I am sure they are very snug and resnugged on the hard. Also, both sides sang -unlikely both slid back.
Until this thread, i've never heard of it. Next trip out, no humm. We will keep listening and will get a cam over to look. (Water is still only 50 and I am sometimes a weenie.) Thank you all!

 

[firstbase]

Went out on boat a week later, less singing. Same tune but not as loud and we didn't touch the volume knob so must be getting broken in or dirtied up a little.