I think I have some encouraging news and learned a lesson to not pull the fire alarm until you see flames.
I cleaned up the area around the crack and then got my video scope in place. After starting the engine, I could see that oil was dripping out, not in the crack, but around the lowest bolt.
I think I just have a rear seal leak. That's much, much better news. I looked in the Moyer Repair Manual and it really doesn't show or talk much about how to replace that seal that I could find.
What I'd really like to see is an exploded view of that procedure and the parts so I can get an idea of what's involved. I'll search here for posts that talk about it. Likely there is a good one somewhere. I have practically no room to work in that area but hope I can do this without lifting the engine of pulling the boat out of the water.
Here's a new video showing the drip. Sorry for the quality but my camera is Harbor Freight quality and aside from that, it's hard to control it.
https://vimeo.com/349197977/305d4be89d
EDIT:
I found Don's PDF that talks about the job. I still want to find an exploded view or something so I can wrap my head around what's what. Regardless, Don's directions are great to have.
Anyone want to rent me some tools? Output coupling holding tool (TOOL_07_136) / Output coupling puller (TOOL_06_135) / Output coupling installing tool (TOOL_08_137) I hate to spend $150 on tools I'll use once. Still, cheaper than having someone come do it, I know...