The short answer is yes. It takes a lot less HP to spin a whipple than it does pretty much any other belt driven supercharger.
The new rotor design on the 3.8 is also very, very efficient.

Brad,
you are correct the blower is very low profile itself,but I had the intercooler also in my kit at the time. My boat was a 2004 Y2K with a 496HO ITS with an XR . the 500/525 hp upgrade at the time was 12k more. I bought with the intention of doing the Whipple for half the cost,installed myself and gained 2x the hp. ,keeping it all under the hatch. Working with Dustin, he sent me a pulley making 7-8lbs of boost instead of the stock kit pulley at 5-6lbs. He remapped my computer and we figured 650hp.. Never had a problem in 5yrs. I did 71-73mph no blower, to 81-82, first pulley/prop. To best of 86.7...,

Based on the cubic inch difference between the blowers it must be much more efficient....289ish for the whipple and 550ish for the 14-71

Love the project! Mines not quite as much of a sleeper as yours since i have a big roots sticking out of the back but I love seeing bigger single engines get some love!! Thing should scoot pretty well!!

nice project for sure ! well done !

Congrats
F.I.L. used to have a 28ZT with 502
Fun ride

Totally agree that is a real deal statement, every word of it!🤙

Just a little more on the 3.8L blower from Whipple...
I LOVED the 3.3 on my personal boat. It never loaded up, shifted like a dream, made 800hp on 91, etc.
But.
I ordered a 3.8 for myself. They really did raise the bar...again!

Cool project.

nice job on the engine guys.

Is the stage 1 also a port injection? What ECU do you use?

Is there data showing how much less HP?

Stage 1 and 2 are both available with port injection. We use Holley HP efi, 555 or Mefi. If a custom build, Holley. If the client already owns Mefi or a 555 (500 or 525 basically) we can use that too.
I'm sure there is data on a graph showing this. But, I can tell you from personal experience. To make 12PSI with a ProCharger, no matter what we did the 12rib belt would slip. We modified the tensioner and everything. The only way we could make it work was switch to a cog style belt. Then, the ProCharger bracket started to bend. It was hopeless. We figured at 12psi it was taking 2-300hp to turn that blower. We had to upgrade from 96lb injectors to 120 just to get enough fuel into it. The OP engine has 63lb injectors in it. Why? We had to make 1200hp to net 1000hp with the procharger. I can spin 2 Whipples (QuadRotor) with one 10 rib belt and one tensioner at 12psi all day long. That's how much easier it is to turn those blowers.
Another downside to that style compressor is it's essentially always trying to make boost. The only thing stopping it is the throttle plate, which is after the compressor. Again, it takes a lot more power to turn it. Even at cruising speed. With a Whipple (or even a roots setup), the throttle plate is before the compressor. So to control boost you control the amount of air being let into the compressor instead of choking down the compressed air going into the intake. At a part throttle setting (cruising speed) you aren't letting enough air into the whipple to make boost, so the compressor is free wheeling. Remember, with any belt driven compressor the ratio between crankshaft speed and blower speed never changes. It's all about the amount of air going into the blower and what you do with it.
There are plenty of people out there making good power with ProChargers. But there's a reason Mercury, Sterling, Teague, myself, ETC refuse to build a new engine with one. Not only are the ugly, but the bracketry is not up to offshore abuse without modification, they sound awful at idle, and they take big power to make big power. The only upside is initial cost. Whipple as a company has taken wonderful care of us. Whenever we've had an issue (and there have been very few over the past 25 years) they've made it right immediately. I cannot say the same about ProCharger who would send me the wrong parts and then refuse to accept the return because we "opened the box".