Back to the Plot Hole
I’ve seen Back to the Future III at least a half dozen times and it just dawned on me that there’s a major (potential) plot hole. The move takes place in 1885, 100 years before the original. Marty and Doc are trapped because the time machine that Marty took back ripped a fuel line and ran out of gas. Putting aside the whole why not just change the speed at which the time circuits activate, they still have the time machine that Doc got sent back in. The can’t use it as is to get back (because the time circuits fried and in any case it would create a temporal paradox and disrupt the time space continuum). But there’s no reason they couldn’t siphon the gas from the first machine to get back in the second. The first would stay put for 70 years until 1995 when they refuel it to send Marty back. I guess if it’s taken me this long to figure that out maybe it’s reasonable that Marty and Doc didn’t think of it.