"in all the specs for the different engines I've see here, everyone talks about the HP ratings on their engines with no mention of torque."
That's because it's all about power to the pump. And how well that power is converted to thrust (impeller efficiency). Torque is for wrenches. Those who claim torque and power are the same don't really understand the difference between the two. They are not the same.
There are racers who've applied max torque to the impeller (with cut size) hoping for best performance. There are racers who've applied max power to the impeller hoping for best performance. You think they got the same result?
No. Why?
Because torque and power are not the same thing. And yes, understanding the difference can be important. You'll read a lot of myths about how torque is more basic and "what a dyno measures" so it must be key? In the end, just myths....often repeated by well-intentioned and sometimes well-respected sources until accepted as fact.
Think about it. What does a dyno really measure?
True, at any given rpm, more torque means more power. But also true...an engine can be built for more low end torque (power) or more high end power. And once built, an impeller can be matched to peak torque or peak power. Those two match points will not give the same performance. So even though Q and Hp are related, how well you understand the physics can make a difference in your jets performance. Power to the impeller is what it's all about. And how efficiently that power is converted to thrust (a factor of cut size among other things) Torque is only half the equation.
jer