On Mon, 19 Apr 2004 19:27:39 +0200, "Anders Lassen"
anders.lassenNEJTILSPAM (at)adr.dk wrote:

Any metal-detectives that can cast (sorry!) a light over the reason?

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The failure appears to be the result of a crack which developed over
time, and gradually incerased in size to the point where there was no
longer enough metal left to support the structural load.

So the question is, what caused the initial crack, and why did it go
undetected for so long? Dezincification is one possible reason. If
you have inadequate electrolysis protection from sacrificial zincs on
you prop shafts, the zinc in your bronze props will gradually
disappear through electrolytic action, and the metal will be weakened
leading to structural fatigue, cracking, and failure.

Another possibility is that the prop was damaged in some way from
striking a submerged object or accidental grounding. That could have
lead to a small crack which gradually increased to a large crack and
failure.

An ounce (28 g) of prevention is worth a pound (.45kg) of cure.