So what happened to my outdrive ?

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bluetooth

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Was midway between Portland and Torquay 20 miles offshore, in 60m of glassy water cruising 3,000 revs at 23/24kts in company. Perfect conditions. Engine purring, boat hardly rocking, me enjoying said perfection gazing forwards scanning seas as usual - no boats, no pots, nothing. Absolutely beautiful !!
Sea.jpg SB.jpg stern.jpg

Suddenly feels like boat has been caught and drag backwards. S##t must have been a submerged pot (but slack tide and no waves or ripples) !
No impact noise/thud, no change in engine sounds but rev counter on one engine goes crazy.
Put into neutral ASAP and radio the boats in cruise and we all slow down.
Engines off and lift drives expecting to see a net or no props but nothing... all looks fine.
Engines back on without problem, engage damaged drive, engine revs as normal but no propulsion!
Second engine fine and engages.

After various discussions we chug on one drive into Torquay.
After initial assessment need a lift out.
At lift out oil plug screw magnet covered in swarf (like xmas tree) and bad news relayed to me.
Both SS props on said drive have been bent/dented as if something got stuck between them.
After leg removed the drive shaft was found to have ... well shattered....

Drive.jpg

So what happened ?
Flat seas, no ropes, no pots, no fishing boats, no branches, no containers, no logs (I was gazing forwards when incident happened) - no nothing to see on surface.
No noise, no thud, just felt like the boat had been snagged.

Thinking some chunk of wood floating below surface that somehow was sucked between props but to bend/dent SS props ? The sudden loss of 3,000 revs converted the damaged drive/stationary props into anchor type drag which gave the effect of being snagged.

Have been in some F6 seas and through pot infested seas and well used to looking out for surface disturbances to warn of possible dangers.
What scares me is what caused this and what I could do in the future.
After 13 years of cruising maybe it was just my turn for the one-in-million chance !!

Any thoughts? Anyone else had similar issue ?

Simon
 
It doesn’t sound as if there was anything you could have done to prevent that.
A small chunk of hardwood floating near the surface could have been the culprit.
 
All sorts in the water. I nearly hit a fridge once. But your incident reminds me of a time a mate and I were returning from a cruise. Exact same symptoms he described. 23knt cruise a bang drag. For me who was following a good 300 yards behind saw a pot buoy a good 100 yards to his starboard shoot towards him. His wife saw one to his port to the same. These two buoys some 200 yards apart were joined together by a sinking rope. It was not enough to bend blades but I think it missed the blades but caught at the cavitation plate and flipped the drives up.
 
No idea what caused it, but its not dissimilar to something that happened to me.

Id left the marina and was accelerating onto the plane when the boat suddenly slowed down, i stopped the engine and tilted the drive up expecting to find a rope or bag etc wrapped round it,but instead found the drive shaft had sheared behind the front prop, the rear prop and remaining shaft had fallen to the bottom of the sea.

I have no idea what caused it. There was no noise, or obvious obstruction, or any damage to the remaining prop,drive casing etc. Thankfully the insurance paid out to rebuild the drive.
 
This happened to me many years ago & was due to the oil absorbing water through a failed seal somewhere in the outdrive. I got it rebuilt but it was never any good. Whoever rebuilds it needs to be absolutely top notch.
 
It's a weird one this. On the basis that the props were damaged, I can only conclude that there was an impact of some kind (as opposed to mechanical failure). On that basis I would expect your insurer to approve your claim and arrange for the drive to be repaired immediately. It's these (edge) cases that separate the good insurers from the bad insurers so if you've had less than perfect service then it would be useful to know who the insurer was (once the dust settles).

Regarding the impact, I can only assume that it was an object large enough to damage the props (probably doesn't need to be more than a small chunk of driftwood) but small enough that you didn't notice it when you drove over it (assuming you weren't taking a photo at the time :)). If it was a sizeable piece of flotsam then it should have flipped the drive up (perhaps saving the props but running the risk of some hull damage).

As for preventing this in the future, I can't see how you could. As you say it's just one of those one in a million things and at the end of the day the damage was limited to the drive, you all got home in one piece and the leg can be easily repaired.

That's boating!
 
bluetooth said:
No impact noise/thud, no change in engine sounds but rev counter on one engine goes crazy.
Click to expand...

That's odd, I wonder why it did that (engine sync should have prevented this surely)?

Also, did you lose power steering or was it the 'other engine'? If power steering was lost then I assume you could have kept the 'bad' engine running in neutral to maintain steering.
 
Happened to me too a few years back, also completely calm seas which I now think was why I did not see or perhaps it increased the odds of hitting the props. There was however a definitive thud/impact noise but in my case the shaft did not shear completely but had to be replaced on inspection.
The SS props were bent though and my takeaway from this was to get aluminum props instead and keep a spare set in the boat thinking this would spare the drive and a lot of hassle if it happened again.
 
julians said:
No idea what caused it, but its not dissimilar to something that happened to me.

Id left the marina and was accelerating onto the plane when the boat suddenly slowed down, i stopped the engine and tilted the drive up expecting to find a rope or bag etc wrapped round it,but instead found the drive shaft had sheared behind the front prop, the rear prop and remaining shaft had fallen to the bottom of the sea.

I have no idea what caused it. There was no noise, or obvious obstruction, or any damage to the remaining prop,drive casing etc. Thankfully the insurance paid out to rebuild the drive.
Click to expand...

I had this in the middle of the sea between Barcelona and Palma. The boat actually ran fine but the RPM was uneven so I knew something had happened. Insurance Paid - about E5000 as i recall including the lifts.
 
When I had a outdrives boat slightly similar thing .
Running fine then one engine slowed and the boat lost speed say 26 knots to 22 .
No noise other than normal .
Managed to soon find a nice shallow 2m sandy bottom anchorage in flat seas .
Lifted the legs and one had that black builders band / ribbon that they use to package bricks with ,all wrapped around .
So I jumped in with a snorkel an attempted to free off .
Ruddy stuff was well and truly jammed in the gap s between the two props and the rear and the gear case .
Very careful I managed ( after reading the owners manual) to remove the props and shims / washers etc remembered the order etc .
Then carefully with a hack saw and Stanley knife spent about 40 mins carefully dissecting the stuff off .
Mindful of the rear seal integrity.
Then refitted the props and shims etc .
Luckily next season at the haul out the oil come out normal - not emulsified.
I was lucky got away with it :encouragement:
 
I can see its a Volvo drive and what is strange that the sudden stoppage broke the shaft and not the shear coupling just below. It has a machined groove to encourage it to break at that point if there is a sudden load on the drive to protect the gears and clutches.
 
spannerman said:
I can see its a Volvo drive and what is strange that the sudden stoppage broke the shaft and not the shear coupling just below. It has a machined groove to encourage it to break at that point if there is a sudden load on the drive to protect the gears and clutches.
Click to expand...

You would think so but no, not always





EAKGIHz.jpg
 
spannerman said:
I can see its a Volvo drive and what is strange that the sudden stoppage broke the shaft and not the shear coupling just below. It has a machined groove to encourage it to break at that point if there is a sudden load on the drive to protect the gears and clutches.
Click to expand...

What part is it that is photographed in the first post, is it what VP describe as the "Propellor shaft" or the "Gear set"? With my limited knowledge I would describe these as the inner and outer shaft.
 
petem said:
What part is it that is photographed in the first post, is it what VP describe as the "Propellor shaft" or the "Gear set"? With my limited knowledge I would describe these as the inner and outer shaft.
Click to expand...

Shaft
Splined sleeve
Counter Shaft
 
A_8 said:
Happened to me too a few years back, also completely calm seas which I now think was why I did not see or perhaps it increased the odds of hitting the props. There was however a definitive thud/impact noise but in my case the shaft did not shear completely but had to be replaced on inspection.
The SS props were bent though and my takeaway from this was to get aluminum props instead and keep a spare set in the boat thinking this would spare the drive and a lot of hassle if it happened again.
Click to expand...

Hm, good reason to have allu props ?
 
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