What the heck, we said. Pull the prop. See what we have. Have the shaft inspected. The engine is two weeks late – what else can go wrong?
The prop is held on to the stainless steel shaft with two bronze nuts.
Rut-roh. Let’s have a closer look.
The pink color is where corrosion has eaten the zinc out of the bronze alloy, leaving almost pure copper. Pure copper is much weaker than bronze.
I’m sure the other one is fine.
The cracks at 1:30 and 2:00 are much weaker than pure copper. Bummer. Well, let’s move on…
The white corrosion at the end of the shaft is easily overlooked in pre-purchase wanderings, but is easy to see once you notice that the prop was about to fall off. Not to worry, though, the shaft was so bent that it had to be replaced anyway. Not a difficult call.
The prop is just fine for a forty-year-old bronze museum piece with inadequate galvanic protection. Corrosion and de-zincification is/was superficial.