Verify your alternator pulley!
 

While rebuilding my spare alternator...
https://986forum.com/forums/performance-technical-chat/87604-rebuilding-alternator.html
... I discovered that the pulley was seized (they are supposed to act like a ratchet, locked in one direction and freewheeling in the other).
So I verified the pulley on my base Boxster that I am selling... and found it was seized also. I bought 2 new pulleys, and installed one in the car. I have now started preparing my Boxster S for its Spring coming out (of storage) and checked the pully... also is seized. Good thing that I bought 2.
That makes 3 seized pulleys out of 3 that I have checked. I am curious to know what other's experience is. I might add that that the pulley on my friend Newart's Cayman also failed, it came apart while driving and threw the accessory belt off, leaving him stranded.

Here they are...

http://986forum.com/forums/uploads02...1773169868.jpg

To remove and install you need these tools, I think they are standard for Bosch alternators.

http://986forum.com/forums/uploads02...1773169892.jpg

Whose pullies, OEM or aftermarket?

http://986forum.com/forums/uploads02...1773175903.jpg

All three are INA F 233525 1

Correct factory part to my knowledge is 997-603-154-01-M40, which is an INA 5350025100, which may or may not be the same part.

https://vehiclelifetimesolutions.sch...TQ4NGFhOGI0ZTY

I feel 1/3 of your pain (cuz I only had 1 boxster with a frozen overrunning clutch on the alternator and you have 3).

When I discovered it, it was because the bearings had also gone south, so the Easy Button was to replace the entire unit. That was after somewhere around 175k miles of year round driving in northwest NJ, so plenty of road salt, etc at play.

According to this chart the Porsche part number is the equivalent of the INA F 233525 1 which. in turn. on other sites is the equivalant to the number that you quote.

http://986forum.com/forums/uploads02...1773235731.jpg

I think it is safe to assume that all three of these pulleys are original from the factory.

I read the INA number off a factory part we happened to have in stock.