Cracked prop!

[holden]

My friend cracked his prop on his Sanger dx2. It's ok, he was a Malibu owner but competes barefoot

And they all run sangers in comp now.

Take a look at this ... Any idea what could of caused this?

Didn't hit anything ... Edge of the prop is clean.

We think this is a remanned prop but only the edges bit an entire blade.

He noticed a slight vibration at barefoot speeds.

After the session he pulled out and they checked the prop ... Didn't see or feel the crack.

Went out a day or two later and vibration was a little worse and at lower speeds.

Pulled it out as he didn't want to take chance and pulled prop to look at it and check the hanger.

When he took prop off ... Voila!

Good thing it didn't separate at speed! We are really curious what might have caused this other than the really obvious manufacturer defect.

[happypappy]

Any metal is good for so many cycles...looks like you met and exceeded the number of cycles.

I have seen the older prop shafts shear off, right behind the strut. Not from hitting anything, but from exceeding the number of times flexed or cycles. Part of the reason boat makers went to the current 1 - 1/8" dia shafts. Athough not a huge increase from 1" to 1 - 1/8" dia, but did increase the cross sectional are by nearly 25%.

[nuttyskier2002]

Yup! I had a whole blade break lose from the hub and I never felt it hit anything. Just all of a sudden it developed a huge shake and I couldn't do more than just idle back to the ramp. I've seen cracks in flywheels and in the main webbing on engine blocks. Doesn't have to hit anything for this to happen.

[Durty_Curt]

was that prop ever previously damaged and then repaired?

[holden]

Yes, the edges were refinished. It had received a few burrs after hitting a sandy bottom.

It was a couple of years ago. I understand metal fatigues but how this cracked is very strange. Although the boat is primarily used for barefooting 2-3 times per week (4 hour sets) and lots of passes at 40+ mph