D) The outback went as fast as the aircraft carrier pulled it.
Could you tell me if the answer is not "D" then why?
Actually the eddy from the carrier would suck the Outback right up to the stern. Ignoring that, D would be right for a couple of reasons.
1. The traditional formula was derived for large displacement hulls, primarily navel vessels. Kayaks and most light boats have semi
-displacement hulls. So the 1.34 formula does not fully apply. "Hull speed" is still there, but the old formula has been more accurately replaced by a Froude number
-- it can vary greatly from one boat design to another.
2. The aircraft carrier has ample power to easily pull the Outback out of its wave trap. As a practical matter though in the trolling electric motor world, simply doubling the power doesn't get you nearly enough to break out of the wave trap. That is what I was addressing originally.
In this picture series you can see the wave trap developing as the PA goes faster. Note how much the stern is squatting in the lower picture:
And that hull speed formula...could you plug in the waterline hull lengths of the Hobie hardbodied, mirage drive vessels to the hull length formula and post the maximum speeds for each.... It would help to see if anyone has broken the Hull barriers.
The "hull speed" zone is easier to exceed in some boats than others. Generally the beamier the boat (for a given waterline length) the bigger the bow wave, the deeper the wave trap, the harder to escape with more power. Other factors come into play as well such as rocker for example. The PA, Outback and Outfitter generate big waves near "hull speed" and have a relatively hard speed limit (without lots of additional power). The Adventure, being longer and narrower, has a much softer limit so the "climb" out of the trap is much gentler and it takes less additional power to go faster.
All the Hobies can exceed hull speed -- it's only a matter of how far and how much thrust is available.
But the real issue here was not the all important hull length rule that IS important for sailing events. The real reason that the guy's hobie wasn't going faster was because the hobie didn't offer enough resistance to impeded the maximum performance of the prop, and virtually the same propeller was on all three trolling motors. The larger trolling motors could probably put a PA on plane IF it had the right prop on it.
It was the mismatched prop that cause the poor performance of that vessel with the larger motors.
You may be right. No doubt the prop has to match the application and it may well be as you said that the prop was topped out at that speed.
But the same result occurs when the boat approaches its hull speed. The bow wave gets so big the power needed to climb up and over-power it is generally not available on our kayak realm regardless of prop pitch. If you notice on the water, the only small boats you usually see going much faster are planing hulls, foils and multi-hulls. For the record, some small sailboats can beat the snot out of any of the Hobie kayaks -- they don't suffer any unique hull speed limitations IMO.
Hope this helps.