Loud Clanging in rear and chipped tooth on Flywheel - HELP!

[Newby]

All went well the last time I ran the boat a week ago. Started the boat on muffs on the trailer yesterday and had immediate loud clanging/banging noise in the rear of the engine compartment. I checked for anything loose or in the exposed portion of the coupler. Nothing. Tried again, the same noise. Removed the starter. The starter drive teeth looked good. Looked in the started hole in the housing and there is a shiny spot on the flywheel and a tooth is missing. Did I just pop a tooth and because of the close tolerance it is bouncing around in the flywheel housing? Or is it possible to have a bolt backing out of the coupler or the flywheel? Is it possible to get a foreign object in there? It looks like it is completely closed to the outside except the external part of the coupler and possibly the inspection plate under the motor. The inspection plate is in place. I plan on puling the motor unless there are any better ideas. The flywheel needs to be replaced anyway! I tried to remove the bolts to the inspection plate, but it is not possible to remove all of them even while standing on my head. Any help would be appreciated.
The boat is a 1990 16C 4.3LX gen II

[Cuda]

I broke the teeth off a top mounted starter on a 454 that wedged down against the flywheel and bellhousing, making the engine impossible to turn over, but I've never heard it the other way around. I'm betting that piece of flywheel is banging around in there. Bad news is the engine has to come out to check. :(

[Pismo]

Pull engine, find all the pieces, may just be able to just replace the tooth ring on the flywheel. That plate on the inside off the bell housing comes off easily so you access the flywheel. Remove flywheel, stick it in the oven, remove old tooth ring, etc etc.

[Newby]

Thanks for the responses. I will let you know after I pull the engine and replace the starter ring if there was anything else going on in there.