The original thread to this was closed.
Here's the answer, the new shop R&Rd or adjusted:
1. Fuel pump
old 7.8V new 18.0V
old 5.8P new 5.5P
2. Carb setting and choke system
Jets 67-68 up to 79
3. Distributor advanced curve
4. Distributor gear
My last failure on this stutter, stall, die problem occurred at 90 minutes. Earlier failures occurred at 45 mins. This shop only had it on the lake for an hour testing their repair, so we'll see.
This problem needs dyno testing to truly isolate the cause(s) I guess.
My first two shops troubleshooting this didn't have the equipment, so they were just barnstorming a best guess, I guess, based upon their experience and an ohm meter.
I hope this helps someone.
My next boat will be a motorcycle.