Alpha one strange plate?

[South563]

I have changed impellers from alpha one gen 2 drives before, but now two of these metal plates dropped from drive when removing the lower unit (for reference the plank behind the plate is a 2*4(4 side up)). From schematics I can not find what the heck these are. Also there was some rubber which suggests that these plates have been connected between the straight edges as a bigger plate.

 

[Scott Danforth]

welcome aboard

those are the remains of your exhaust shutters.

looks like you ran out of cooling water and burned all the rubber bits.

I would check the inside of the rubber exhaust hoses as well. in addition to the two sets of flappers, you most likely need new rubber exhaust hoses.

 

[kulle]

what is with these shutters ! LOL seems like thread after thread. Speaking of shutters....when I found that piece in my exhaust I ordered the new designed replacement part. When I went to install the port side, there wasnt even one in there ! Now a question is, could a missing one possibly have caused some of m intermittent shut off issues or would it be more likely the piece if shutter lodged in my exhaust? Didnt know if water potentially could have got in through that valveless exhaust riser and into engine?

 

[poconojoe]

Yep, exhaust shutters...been there, done that. As stated, finding them where you did means at some point your engine was overheated.
They sit inside the vertical section of your exhaust after the downward elbow and pivot on a shaft. They are encased in rubber. The rubber melts and they fall down inside your exhaust. As you found, they can even work their way all the way into the stern drive.
They prevent water from backwashing into your engine which can cause hydrolock. This can break or bend things in extreme situations.
If you're cruising along and have to power down suddenly, a wave can hit the stern of your boat, flooding you exhaust system. The shutters come into play.
There are many different styles and sizes, so look closely at your old ones for comparison shopping. If you're lucky, there's a part number on them.