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Old 01-21-2024, 08:13 PM   #1
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Singing prop? Cutless bearing?

Slightly long question - bear with me.

We finished a haul out - glassed over some thruhulls, replaced engine seacocks/strainers, bottom paint.
Most important - BOTH props were pulled, tested and all 8 (2x4) blades were at various degrees out of spec. Props sent out, all fixed and we splashed. During the initial in-the-harbor seatrial (low RPM) there was a ghostly humm - turned out we had singing props (boat yard originally suspected cutless bearings). Prop shop admitted that they usually put 'anti-singing' edge on the props but had forgot. All done, back in the water. Singing apparently gone.
When we went out for a longer seatrial - at around 1500-1800 RPM on the port side only, we get a loud constant squeal (doesn't change pitch with increased RPM). Audio file (on Dropbox - no account needed).
Again the boatyard is suspecting the cutless bearings.

Observations:
1) Port side only, only between 1500-1800RPM and under load
2) Noise from outside under boat - loud in rear lazarette and aft cabin, audible from fly
3) Not audible from inside engine room

Questions:

1) I've searched this forum and not read any associating a sound with bad cutless bearings
2) Thoughts on whether this is still some remnant of the singing prop issue?
3) Has anyone passed the feeler gauge and shaft lifting test only to still find the cutless bearings bad?
4) It seems reasonable to replace all 3 bearings on the port side - any reason to also do stbd side at the same time?
5) On scale of 1 (a minor annoyance) to 5 (you'll likely score your shaft if you keep using it) where would this fall in your opinion?
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Old 01-21-2024, 08:27 PM   #2
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When the cutlass bearing went bad on our boat it sounded more like a rumble. Luckily it happened on the way to the boatyard and that repair was added to the list. Also you could see and feel the play in the driveshaft when wriggling the prop.
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Old 01-21-2024, 09:31 PM   #3
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A bad cutless bearing does not sing, it rumbles and in any case it’s very easy to check a cutless bearing. It’s almost certain to me that you still have some prop singing.

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Old 01-21-2024, 09:45 PM   #4
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I wonder if the shaft is out of alignment? That might make a squeal.
By the way, it is Cutless not Cutlass.��
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Old 01-21-2024, 10:39 PM   #5
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There are specs for the gap. You can measure it with a flexible feeler gauge.
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Old 01-21-2024, 11:12 PM   #6
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I would put my money on the props still singing, perhaps they didn't take enough off the leading edge. Doubtful a cutless will make that sort of noise unless it's running way out of concentricity.
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Old 02-10-2024, 10:57 PM   #7
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@lwarden for the win!
We hauled again - no one could feel anything amiss with the shafts/cutless bearings. Shafts turned easily.
Had the prop guy out who took a grinder and shaved a bit more off - splashed - and all is good.
A rare - 'saved some boat bucks' - day.
Thanks for all the responses.
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Old 02-10-2024, 11:21 PM   #8
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Glad you found the problem.
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Old 02-11-2024, 08:44 PM   #9
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Sure is a weird phenomenon that's humbled even some seriously salty folks. Glad you got it sorted.
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