Rattle from prop shaft - any ideas?

MattS

MattS

Well-Known Member
Joined
7 Sep 2020
Messages
570
Location
Kent
Visit site
Does anyone recognise this rattle which seems to be coming from the prop shaft / stern gland area?

HR352 - Noise from prop shaft 1

HR352 - Noise from prop shaft 2

Boat is a Hallberg Rassy 352, with a Volvo Penta engine.
Stern gland is a Volvo dripless shaft seal
Folding prop

At low revs / tickover but in gear, the rattle seems to disappear.
When you start putting the revs on, this noise appears.

Nothing obvious in engine compartment, and all sounds usual. Videos taken in aft cabin, and noise is most audible from aft cabin but also in cockpit.

Wondering if it's one of those noises that others will recognise immediately and go "oh that's clearly blah..." Could it be cavitation potentially?

Thanks!
 
I had a similar noise when the prop shaft moved forwards in the under-torqued split-halves coupling bringing the rope cutter right up against the P-bracket.
 
Last edited:
MattS said:
Does anyone recognise this rattle which seems to be coming from the prop shaft / stern gland area?

HR352 - Noise from prop shaft 1

HR352 - Noise from prop shaft 2

Boat is a Hallberg Rassy 352, with a Volvo Penta engine.
Stern gland is a Volvo dripless shaft seal
Folding prop

At low revs / tickover but in gear, the rattle seems to disappear.
When you start putting the revs on, this noise appears.

Nothing obvious in engine compartment, and all sounds usual. Videos taken in aft cabin, and noise is most audible from aft cabin but also in cockpit.

Wondering if it's one of those noises that others will recognise immediately and go "oh that's clearly blah..." Could it be cavitation potentially?

Thanks!
Click to expand...
Is there an Aquadrive fitted?
 
Can you get a picture of the gearbox coupling and prop shaft running. I suspect it is a problem at the cutless area. Do you have a rope cutter? Is there any evidence inside the boat at the shaft seal that the shaft has moved forwards?
What type of folding prop?
Might be worth going for a swim with a pair of goggles on !
 
I had 3 events that caused 'rattles' :

1. One of the engine mounts failed and allowed engine to move - sounded like a tin of nails !!
2. Picked up a piece of net going past Folly Inn .... thought the transom was going to fall off !
3. My Gator rope cutter on shaft - the holding bolts into the prop shaft tube sheered allowing the static part to rattle on the shaft ... sounded like a bell ringing under there !
 
Usually in higher revs only as Refueller says it’s engine mounts or worn folding bearing .
Engine mount came loose on one side on Paddy ,really shook doors open down below in higher revs.

Another boat I looked after with 20 yr old max prop had nasty noises in higher revs because the internal locating teeth were worn .

.
 
Either something at the coupling end or the cutless. Doubt there is an anode on the shaft as there is no space for one aft of the cutless housing.
 
MattS said:
Does anyone recognise this rattle which seems to be coming from the prop shaft / stern gland area?

HR352 - Noise from prop shaft 1

HR352 - Noise from prop shaft 2

Boat is a Hallberg Rassy 352, with a Volvo Penta engine.
Stern gland is a Volvo dripless shaft seal
Folding prop

At low revs / tickover but in gear, the rattle seems to disappear.
When you start putting the revs on, this noise appears.

Nothing obvious in engine compartment, and all sounds usual. Videos taken in aft cabin, and noise is most audible from aft cabin but also in cockpit.

Wondering if it's one of those noises that others will recognise immediately and go "oh that's clearly blah..." Could it be cavitation potentially?

Thanks!
Click to expand...
We have similar set up except solid three blade prop, and had a similar noise last weekend. I have dived and scraped off propeller blades and noise stoped. Propeller was really fouled ...
 
Pye_End said:
How do you assess the engine mounts in situ, apart from visual?
Click to expand...

Generally you cannot. You can onlyu observe the engine move when throttle applied or starting .... those two 'events' show movement.
To replace - it is recc'd to replace all mounts = not just one or two.

Mine needed complete hard wood bearers removed as whoever installed the engine used headed bolts inserted from bottom of bearers then to engine ... whole lifted into place and bearers fixed. This meant that it was impossible to replace mounts without a total engine out ...
We replaced with heavy iron angle so in event we ever needed to work again - it was easier. Was actually fortunate as few years later - we had to change engine.
 
What sort of gearbox do you have, and have you checked the oil level? I've heard exactly that non-rhythmic 'clattering' before on a Yanmar - turned out to be chronically low oil on the Kanzaki box which was affecting the clutch cones.

If it were a shaft anode or rope cutter issue I'd expect a more rhythmic sound.
 
Major_Clanger said:
What sort of gearbox do you have, and have you checked the oil level? I've heard exactly that non-rhythmic 'clattering' before on a Yanmar - turned out to be chronically low oil on the Kanzaki box which was affecting the clutch cones.

If it were a shaft anode or rope cutter issue I'd expect a more rhythmic sound.
Click to expand...

I can tell you that a rope cutter when free is definitely not rhythmic ! Its like a madman with a bell ...
 
Thanks everyone for the suggestions - loads of useful things to rule out here. It's a friend's boat, so I don't have direct access - but hoping he can gradually rule out each of these issues.

He's already checked the gearbox oil, which seems fine - so hopefully that's one down!
 
Tranona said:
Either something at the coupling end or the cutless. Doubt there is an anode on the shaft as there is no space for one aft of the cutless housing.
Click to expand...
There is an anode on my shaft in the same boat. So it could be a loose anode or rope cutter.

I have heard similar on another boat when the folding prop was not opening properly, but that was obvious by the lack of propulsion...but it did resolve itself at high revs.
 
I had something similar earlier this season with noise at cruising revs plus a different vibration. Replaced 14 Yr old mounts and realigned and all good for now though I will have worn the cutless. I measured the before and after height and it was many mm different after realigning.

For me it is now reasonably easy to split the shaft from gearbox and check the alignment for the future. Can you do this and eliminate alignment from the situation?
 
Just to show what happens when Gator meets something it cannot cut !! We suspect that a wire / cable got picked up and the mount bolts sheered when it could not cut ....

N0EjXEc.jpg


You can see that the fixed part has revolved and is free to rattle ....
I removed the fixed part that had sheered its bolts and now only have the section mounted on the shaft. Its obviously noty as effective now - but has cut a rope since then.
 
You must log in or register to reply here.

Share this page

Top