Super Jet Check out this Double Impeller

[T Curtis]

850 cc Dasa with 148 mag skat trak pump

 

[NVJAY775]

Here's a link that tells how they work.
http://www.lawrencepumps.com/newsletter/news_v01_i2_july.html

 

[Midlake Crisis]

the old jet boats from the 70s with big blocks and super chargers used that set up

They are being re-hyped again now. The feedback from actual users on the jet boat forums has not been that great. Definitely not a "wow!", maybe a little extra something but not a big change.