High speed prop wrap!

[Jim Robinson]

A customer of ours hit a pot marker as speed this week. He was able to recover the prop which was knotted in the rope.

[jyasaki]

Sheared the prop shaft? That's impressive.

jky

[Hightower]

Ouch!! On the plus side the prop doesn't look too damaged.

[Doug_G]

Shouldn't the rubber' in the hub have sheared and the shaft left intact.

Why did the shaft snap?

[Jim Robinson]

I would have expected the bush to break not the shaft to break.

[Hightower]

It wouldn't have been a sudden impact type force but a more gradual force as the rope tightened it's grip thus sealing the prop shaft's fate. Was there any sign on the fail point of a previous damage/fracture Jim.

I once had a crankshaft break on an old Evinrude 40 twin off of Bembridge. It had been failing for quite some time until it met it's end. I offered it to my local technical college who showed it to their students as an example of metal fatigue brought about by vibration.

[Jim Robinson]

Looks like it has sheared on a joint. I think the spline is friction welded to the main shaft at that point. The pattern of the rope is imprinted in the paint of the prop.

[Peter_C]

All of the shafts that I have held in my hand, mostly from outdrives, are one piece, that the splines are cut into.

You wouldn't happen to have a close up picture of the end of the shaft would you? Looks almost like it was failing previous to this event, but the photo is not very good on my computer.

[Jim Robinson]

Yep would agree with you peter, but it is such a clean shear like a knife cut

[A1an]

Didn't a similar thing happen to a members Verado? Looked identical.

[Searider]

If you need to know for sure, Send it to Materials Technology in Totton.
They can have a proper look at it.

Fast fracture - probably caused by the rope.
Fatigue failure - possibly initiated by out of balance / damaged propeller over time.
Friction weld failure - maybe down to manufacturing defect.

[Boatnomad]

Hard to believe,something way wrong their?

[Jim Robinson]

Bit better picture of the break.

[CJL]

Another high speed prop wrap.

This was on one of the Thames Clippers!!

CJL

[Peter_C]

Originally Posted by Jim Robinson

Bit better picture of the break.

From my perspective the rusty middle part had been severed before this event. Maybe this is not the first prop strike, or maybe it is just a failure of the metal? Doesn't really matter it just needs a new shaft installed. To a pro it shouldn't be too bad of a job, unless there is a lot of corrosion in which case it could get ugly.

[Jim Robinson]

It a year old so off for inspection by the warranty team. Love the tyre picture.

[Doug_G]

Originally Posted by Jim Robinson

Bit better picture of the break.

Is that 'old' corrosion in the centre, or corrosion that occurred between the time the shaft broke and the picture was take?