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Prop dropped off - what might have happened?

PurpleKate

Member
Joined
6 Jan 2009
Messages
205
Location
Solent
Anyone got any thoughts about what caused my prop to drop off yesterday.
I have a Jeanneau SO36i with a 3blade folding prop (Flex-o-fold). Here are a few clues....

Boat was out of the water 2mths ago for annual maintenance and the cutlass bearing was replaced.
I motored back from Eddystone in the fairly rough easterly winds for about 20hrs on Friday night, 3100 rpm, cruising speed limit on my Yanmar 3YM30 is 3400rpm

The only positive in all this is at least she lost it whilst moving off the fuel pontoon close to home rather than somewhere less convenient like half way across Lyme bay.

Was is bad luck? too much motoring or do I need a conversation with the boat yard ??
Kate
 

sailorman

Well-known member
Joined
21 May 2003
Messages
78,204
Location
Here or there
Anyone got any thoughts about what caused my prop to drop off yesterday.
I have a Jeanneau SO36i with a 3blade folding prop (Flex-o-fold). Here are a few clues....

Boat was out of the water 2mths ago for annual maintenance and the cutlass bearing was replaced.
I motored back from Eddystone in the fairly rough easterly winds for about 20hrs on Friday night, 3100 rpm, cruising speed limit on my Yanmar 3YM30 is 3400rpm

The only positive in all this is at least she lost it whilst moving off the fuel pontoon close to home rather than somewhere less convenient like half way across Lyme bay.

Was is bad luck? too much motoring or do I need a conversation with the boat yard ??
Kate

a conversation with the boat yard
first thing tomorrow ;) then your insurers
 

Fr J Hackett

Well-known member
Joined
26 Dec 2001
Messages
41,209
Location
Grenoble
It should have been fitted with a locking tab, split pin or some other device to secure the nut holding the prop on the shaft, not familliar with the prop so can't say which. However as Sailorman says the Boatyard who did the work must have responsibillity for the integrity of their work however it's odds on that they will try to wriggle out of it thats where your insurers should come in. Try to get a diver to recover the prop to show there has been no damage to it. I bet that's the first thing the boatyard will say. Good luck.
 

PurpleKate

Member
Joined
6 Jan 2009
Messages
205
Location
Solent
yes I was springing off the fuel pontoon into 16kts blowing me on, astern kicked out the bow then when i engaged forward there was a clunk - not the normal clunk a somewhat different clunk and no forward propulsion
 

Fr J Hackett

Well-known member
Joined
26 Dec 2001
Messages
41,209
Location
Grenoble
he prop retaining nut has not been secured the force of the prop has undone the nut, the prop has then slid off the key.
 
Joined
7 Aug 2006
Messages
4,264
Not such a silly question as it might sound ... are you sure that the prop has actually fallen off ?

I once helped tow a boat in who thought his prop was gone but in fact the key that held it to the shaft had sheared = shaft rotates, prop doesn't.

ps

I'm assuming that your boat doesn't have a Volvo saildrive ... the inner rubber bush on the prop can separate on those which gives no drive.
 
Last edited:

PurpleKate

Member
Joined
6 Jan 2009
Messages
205
Location
Solent
good idea but unfortunately the lovely man from sea start had an underwater camera and the prop is gone
 

Spyro

Well-known member
Joined
18 Jan 2003
Messages
7,578
Location
Clyde
Depends on how they replaced the cutless bearing. They could have removed the prop and slide the bearing out (most likely) or they could have removed the shaft with prop still attached. I would ask them first how they did it without telling them why.
 

snowleopard

Active member
Joined
16 May 2001
Messages
33,649
Location
Cornwall
It sounds very much as though the prop was fitted incorrectly. At least you should be able to find it again. A couple of years ago one of my Flex-o-folds shed a blade while anchoring in the Scillies and I had to buy a new set.
 

BlueSkyNick

New member
Joined
29 Apr 2003
Messages
11,770
Location
Near a marina, sailing club and pub
tHIS happened to friends of ours while in Treberden. They carry a mini SCUBA set on board, and were able to find the prop and retaining nut in the mud. Fabricated a locking tab, and off they went.

Maybe worth getting a local diver to see what he can find - cheaper than buying a new prop.
 

pwc51

New member
Joined
23 Apr 2003
Messages
51
Location
Dorking
Happened to me many years ago with a two blade folding prop. It must have happened as we were entering a marina berth that we were visiting. I thought our approach was a little faster than usual but did not think much of it and did not notice until we came to leave the following day! Owing to soft mud on bottom and uncertainty as to exactly where it had fallen off we were advised there was little chance of a diver finding it.

Most likely scenario is that the locking key had failed due to poor anodic protection, but we'll never know for certain. Always protect with two shaft anodes these days and have not had a problem since (plus occasional checks are made to ensure there are no problems).
 

SAMYL

Well-known member
Joined
31 Aug 2009
Messages
1,536
Location
Gone Fishing
I fitted a supposidly stainless split pin supplied by the local chandler to my prop nut and it was gone three months later. I don't know why, there was no trace of it, not even some rust. It must have corroded away or been eaten by galvanic action.
Luckily the prop/nut was tight emough and stayed on.
 

Jeannius

Member
Joined
30 Jan 2004
Messages
595
Location
Worcester, U.K.
I've lost 3 props from my Volvo saildrives. They have a pretty stupid design that seems to guarantee failure unless you do as I do... slosh large quantities of 3M 5200 sealant/adhesive on the shaft. All the ones that fell off were fitted by 'professionals'
 

savageseadog

Well-known member
Joined
19 Jun 2005
Messages
22,401
There is or was a situation with poor bonding on the hubs of Radice saildrive props. There is a rubber shock absorber between two halves of the hub. The rubber unbonds and the outer hub simply slips off complete with blades when in reverse.
 

earlybird

Well-known member
Joined
18 Aug 2004
Messages
3,607
Location
Cumbria; U.K.
For a shaft-drive Flexofold, such as the OP has, the prop. retaining nut is locked by a socket-head grub-screw, which itself is secured with Loctite.
Assuming the prop. was removed for bearing replacement, as seems likely, it may well be that the grub-screw was either forgotten about, or the Loctite, if applied at all was onto a wet or dirty thread surface, with the result described.
 
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