Not gonna lie, I'd love to tumble around a rapids course in a space capsule

That was a ridiculously long post with so many practical errors on how mechanical and ride systems need to actually work. 
 

It’s not a tractor in a paddock or a dam water pump. You can’t just bang it on a contractor and use a couple hundred dollar clutch on the drive she’ll be right. 
 

I’d suggest learning a lot more about how ride control and mechanical systems are put together before giving such a lengthy technical analysis and set of instructions again. 
It’s also laughable that you think the rubber rings for the rafts are some kids inflatable. 

There is a major flaw in your analysis.

2 groups of passengers vary in weight a LOT. 
2 rafts carry differing levels of water onto conveyor, which varies the weight a LOT. 

How do you calculate the minimum force? raft fully loaded to the maximum carrying capacity, then filled with water?

You are assuming that the amount of torque generated to pull a fully weighed down raft out of the water and up a hill would not be enough to lift a raft from a horizontal position on the run out. Remember, the lifted raft was pushed off the conveyor, bumping into a stranded, empty raft on the steel rails of the runout, using the empty raft as a make shift ramp, pushing the loaded raft up to the point it could be caught in the gap at the end of the runout and pulled down into it by the conveyor. It used the other raft for leverage to help invert it and from reports it happened very quickly. 

Without being too gruesome, an average height adult often sits with head above the seat backs of the raft. The report makes it pretty clear what happened to people stuck in their seats and those ejected from the raft into the water. 

You are also assuming that these motors don't already have current limiting. 

...and all of this analysis assumes that things were built using particular specifications, when in actual fact the ride was built on the basis of 'copy that thing overseas by sight without technical specs, and make it work' - so pumps, drive motors, conveyor slats, chains, etc were all obtained or made based on what 'should do the job' and then when things didn't, they improvised - for example, by lightening the conveyor load by removing slats, instead of finding alternate, lighter slat options that would still keep the similar specs to the overseas models imitated.

Rails in the station trough. rails pre-conveyor. shutdown of the turntable load system.

The 'rats nest' of wiring under the operator's console is a testament to the bodgy, piecemeal job that it was.