As was stated earlier:
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Originally Posted by GWC
In a word: Torque
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I'd say torque for acceleration, power for speed.
Torque is a force and Newton wasn't kidding when he said F=MA or turning it around, acceleration = force (or torque)/ mass. I don't know the torque #'s for the Mount (and what, if any, gear ratio is used) but they must be large to move that ship. Power is the rate at which work is being done and HP = torque * RPM * conversion factor. The conversion factor is a number that scales ft-lbs & rpm into HP, or newton-meters & rad/sec into watts, or whatever, depending on the units you're using. So relatively low HP can still move big masses (high torque) but the RPMs will be low. The acceleration of the Mount is also pretty slow when compared to a typical boat. Even a low torque engine could theoretically move the Mount but you might only gain 1 mph every hour.
As for theoretical top speed, I recall the approximation that hull speed (knots) is 1.33 * square root (waterline length). I'm not sure what the LWL is for the Mount, mebbe 200 ft or so ? So that's about 19 knots. With a lot more HP you can go (slightly) faster and perhaps the Mount is more "draggy" that typical so it might top out lower than predicted. Could also be that the prop pitch and gearing is such that redline is hit before max "hull speed". I dunno. Anyone know what the redline on the Mount is ?
For more that I care to know, you can look
here. Using their formulas I get a delivered power requirement of 628 HP for the Mount to do 18.8 knots. Given the losses in the prop/water coupling and then in the gearbox/transmission, the HP needed at the engine is at least 20% higher. So, contrary to expectation, the Mount's twin ~650 HP engines appear to adequate (given the ballpark nature of my calculations) to overcome the water's friction (drag). Kinda surprised me too.
The residual HP (1300-[628+20%]) can then be used to fight the resistance that comes from making the wake(s). I leave it to the reader to calculate how much HP is needed to overcome wake resistance (and yes, there will be a quiz in the AM).
ps - During one of cruises I asked one the Mount's crew what her top speed was and the answer was about 14 knots or a little over 15 mph. Not sure what typical cruise speed is.