Planing boat water displacement

[BartW]

That much is understood. I am thinking more in lines of how much water has actually been moved. Lets say in the instance of the bow rider is at that speed is displacing 500kg of water. But it's travelling at 30knts or 15ms. So every second it displaces 7.5 tons of water. This is where me and maths become really shaky but that seems a lot for a ~130hp motor unless something else is occurring.

this is a small bowrider, about 1500kg displacement ?
in planing mode it displaces less than 500kg i think,

remember It just produces a "dent" in the water surface, it does not "lift" that weight of the water,
I don't know how to calculate the power to produce that dent,
but in your example it would be 130 hp, or approx 100Kw ;-)
or 100KJoule every second.....