Bravo boat over heated, towed home, opened up pump, impeller looked fine, all blades intact. Issue was the center shaft had spun the hub of the impeller. Lots of melted plastic on shaft that had to be removed. New impeller slide on after clean up, all good now but never seen this before, wonder if anyone else has?

Check the color of the shaft again...if its still bright stainless steel looking then its a head scratcher...if its starting to turn dark in color like if it was stained by coffee but still looking stainless then you may have a bearing going bad in the pump and generating heat that travels through the shaft into the impeller hub...

I have seen it probably 2 times in 40 years. Put in new one and worked fine, if I'm remembering correctly

I've had this happen.

I have not. Merc says to replace every 3 years or 300 hours I believe. (whichever comes first).

was it knock off china crap or the Merc.......

Yes. Many of the cheap copies are not fit for purpose and some won’t even survive the first start. Genuine merc for me.

Yep. And on top it off knocking off the packaging is easier than knocking off the part. Skip Amazon.

It's getting hard to tell knock offs from OEM so I've started only buying from legitimate Merc dealers.

Don't ask me about my Chinese Shift cable boot that tore and left a huge hole in my boat......

I replace mine every spring with about 15 hours on them. Most years they are fine, but I've had one or two years where I was VERY glad I replaced them.

I used to replace them every year. Now I just remove them at the end of Summer to let them relax. If they look good, I'll reuse them. I also deburred/champhered the housing ID. The impellers look much better at the end of the year now. I buy everything from BAM.