Weird shaft sounds when spooling down

[unbusted67]

https://youtu.be/xl7sn9D8BMc

I’m wondering if anyone could help me Identify this sound. This is me coming out of gear. It is a cyclical rubbing sound that slows as the shaft free wheels and slows through the water. We’ve just replaced the transmission but the sound was happening with the old one as well. Cutlass bearing looks to be in good shape.

[unbusted67]

I guess I’ll go eat worms then 😂

[tkeithlu]

I've listened. Give me a minute.

[tkeithlu]

Let me make sure I understand. This is the sound of your prop shaft and prop free-wheeling when you slip into neutral gear, right? It's independent of the engine and transmission, right? The same noise occurs when you are in gear, right?

Sounds, within the limits of a lousy laptop sound system and my being hearing impaired, like your prop is rubbing against part of the boat, or a bearing is shot to hell. I recommend that you grab your mask and fins and take a look under your boat.

[unbusted67]

Originally Posted by tkeithlu

Let me make sure I understand. This is the sound of your prop shaft and prop free-wheeling when you slip into neutral gear, right? It's independent of the engine and transmission, right? The same noise occurs when you are in gear, right?

Sounds, within the limits of a lousy laptop sound system and my being hearing impaired, like your prop is rubbing against part of the boat, or a bearing is shot to hell. I recommend that you grab your mask and fins and take a look under your boat.

So this video was shot the day after relaunching and a full investigation out of the water. Cutlass bearing is in good condition and prop and shaft were manhandled to detect play. I am totally at a loss. Maybe it is some growth inside of the dripless gland. Thanks for weighing in.

[Wotname]

WAG

Seriously bent shaft (inside the shaft tube) or serious alignment problem (broken engine mounts)???

[waterman46]

I didn't see a very important piece of info: is the boat underway when you hear this sound or does it also occur at the dock? It sounds a little like its simply the prop freewheeling with boat movement.


How long does this sound last? Does it do the same in reverse? All important data missing.


But I assume you are at the dock, then why does it take that long for the prop to stop turning? Check the prop shaft rotation inside the boat when you switch to neutral. Maybe the "neutral" does not fully disengage immediately.

If that looks OK then have a look at the running gear underwater (with engine stopped of course!) to see if your prop, it's attachment to the shaft and cutlass bearing play are still good.


I doubt a bent shaft, if the boat has normal small or no vibration in forward and reverse.
If its a bent shaft then the boatyard may have done this during the lift out or back in.

[waterman46]

After re-reading your post, you are saying "as the shaft free-wheels and slows through the water". Does that mean you are underway with some boat speed when you go to neutral? Then that must be just the prop freewheeling or the tranny slipping, if you have no bad vibration or other unusual sounds in forward and reverse gear.

[kryg]

This seems like it could be a prop shaft zinc anode is loose and spinning around the shaft?

Originally Posted by unbusted67

https://youtu.be/xl7sn9D8BMc

I’m wondering if anyone could help me Identify this sound. This is me coming out of gear. It is a cyclical rubbing sound that slows as the shaft free wheels and slows through the water. We’ve just replaced the transmission but the sound was happening with the old one as well. Cutlass bearing looks to be in good shape.

[Ninedotsix]

Sounds like the noise may be from seal, stuffing box, cutless bearing.
Good cutless bearings will make noise, even when wet.
Unless I'm all wrong and you have something up the stern tube, there doesn't to me seem to be much here that I personally would be concerned with.
Whatever it is, it may be providing the friction that finally stops the shaft, so I'm thinking stuffing box packing rubbing on shaft. Cheers - 9.6

[jamhass]

Shaft brush?

[S/V Adeline]

To me, it sounds like the shaft is slightly out of line. Possibly at the transmission coupler. A small misalignment at the transmission end could cause a wobble in the cutlass bearing. Definitely sounds like something is making/losing contact during the rotation.