Stupid question
 

I know this is totally lame, and that I should know this, but I just can't decide. I need to know the real deal.

What is the purpose of the tubes that you sometimes sticking up into the air from the prop area of some high performance drives.
I originally decided it was for roostertails, but have since seen boats with them nunning and no rooster.
Help aeriate the prop? If so, why? Seems like that would reduce effectiveness.

Yup,thats it, with 5 and 6 blade props they have a hard time getting boat on plane because prop grips water a little too well, by introducing air lets prop slip,engine builds rpm and boat comes up on plane. Once going fast that part of drive is out of water so it no longer affects anything