That often happens when you loose a sea pump impeller

ooohhhh...that isn't good!

The boat was new to me last year. Ran fine for the summer season, never hot. Impellers were changed this year with winterizing. Old ones had some wear, but not bad. I'm assuming I should try and pull out the old rubber and watch for heat issues?

And any idea on the metal piece?

Ayuh,.... Pull the lower unit off the upper, 'n fish out the broken bits,......

Then pull the elbow off the top of the y-pipe, 'n replace the shutters,....

Yep. You lost Y pipe flappers (metal) and you sent a piece of impeller or something thru the system.

Fish/pull/yank/tug whatever you can out with pliers.
If you can run wide open throttle with no overheating, then you don't HAVE to bother with further disassbly. You MAY still have impeller pieces trapped around in your cooling system but as long as you don't see any overheating you can wait until the next impeller change. Be sire to backflush everything when you do the next one. Pieces can get trapped in the thermostat housing, exhaust water check balls, any coolers, etc.
You ought to replace the flappers, too, as they help prevent water reversion into your cylinders. But since boating season is here, keep and eye on Temps. Buy yourself a $35 Harbor Freight infrared heat gun and shoot all of the exhaust jackets and elbows to make sure nothing is starving for water, and truck on.