OEMs use Roots blowers because they are cheap. It is also an advantage to them that the intake, intercooler and blower are basically one assembly. They are much less efficient than centrifugal blowers, and their mounting position restricts intercooler efficiency.Here is some info on Roots vs centrifugal.1) Dean Nickerson originally had a B&M 250 blower making 650 HP on a 496 engine. With a bigger Roots blower he might have made 700 HP, but instead he switched to a centrifugal blower and made 850 HP. Then he added an Rtech supercooler and made 950 HP.2) We recently replaced an dual carb 8-71 system on a 555 CID aluminum head engine with solid roller cam. With the Rtech system, one Nickerson carb and less cam timing the boat picked up 7 mph.3) The attached graph compares the HP curves of two similar boat engines. The Roots is "state of the art" with intercooler and twin carbs. The centrifugal is "state of the art" with an intercooler that is about 4X the size and EFI.Yes, the centrifugal can and does use more boost on pump gas. It can usually use less cam for the same HP, and doesn't need to make the same compromises on compression ratio, fuel and timing. As a result they are much more civilized around the dock or idling through no wake zones.As far as power band, remember that most boats operate between cruise and WOT. Cars are also quickly brought into higher RPM range when racing. Both cars and boats have limitations on how much torque can be applied at low speed before tires spin or props blow out or drivetrains break.Looks and sound are pretty much in the eyes and ears of the beholder. You might get a dyed in the wool Roots guy to jump to a screw compressor because of the similar mounting position, but the centrifugal is a stretch, and twin turbos are just too far off the beaten path for him to even consider. So I can't help wondering what the Roots guys will think of this...
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