1st step is to isolate all the blk/y stripe wires. Ohm them you are looking for an open to the other power pack. That will be the broken wire. If no broken wire found check the ground path from the power pack that's not shutting down.
I suggest you go through all your wire connections. Use a wire brush or sand paper and get them shiny clean and retest. No wing nuts either. Use a wrench to tighten battery cables. Anyways, that's where I always start. After that isolate battery cables and ohm them. Post length and ohms...
Well, 1st things 1st. Compression and spark test. Report the results. Verify that all 4 cylinders are firing.
Only after you determine that you have a properly working motor do you worry about propping.
Those old glastrons are prone to be waterlogged. The floatation acts like a spong and...