AA versus A versus ?

[clownpuncher]

What's the diff between these impellers? What speed would you expect at say..4000 rpm's. And finally, what would be the optimum set-up with each? Sorry for the dumbass questions, but I bought a boat a few years back and I specifically remember the guy telling the boat had a AA impeller (Energized Jacuzzi) Thanks in advance. I'm always learning here.
http://www.***boat.com/image_center/data/500/536Pdrm0032-med.jpg
[ May 27, 2003, 09:07 PM: Message edited by: clownpuncher ]

[MikeF]

An AA will move more water into the bowl at a given rpm then the A will.
This will give you more water moving out the end of the nozzle and give you a higher speed at that rpm.
The freer your hull slips across the water, the greater the gain in speed.

[clownpuncher]

Thanks for the info Mike. But why would someone pick one over the other? If the AA will move more water wouldn't that be better? Or do you need lots of HP to use it efficiently? Can you tell I'm lost?

[DUCKY]

An "AA" puts more load on the engine, and also produces more thrust than an "A" The key is to choose the impeller that allows your engine to operate in the range that it is cammed for. "AA"'s were usually found in larger, heavier boats (21+ feet, with 455's and 460's)that needed more thrust to get them out of the hole, and subsequently did not need alot of rpm. I remember a 23' Sleek I worked on once with a 460 Ford "Pack-a-Jet" and AA impeller and the owner said it turned 4000 rpm at wot, since the day it was new.

[MikeF]

clownpuncher:
Or do you need lots of HP to use it efficiently?Pretty much!
If you are able to turn that big a wheel...then you are putting out some GOOD! power at 4500-5800 rpm. The pump has to be tight though to make the most of it. If the pump is loose, the #s won't make sense.

[clownpuncher]

I think it's starting to penetrate my thick skull. Thanks for the explanation. So if I work backwards, would I be able to approximate my 460's hp? It's an 18' Challenger that turns at least 4000 rpm's. I say at least becasue I was too chicken$hit for WOT. The guy did tell me it was cammed right and yada yada yada (valve train this and pistons that).
I was so green when I bought the boat. When the gear head was telling me all about the boat, engine and pump I think I looked like the little dog with his head tilting when he heard his masters voice. You know the picture right?
[ May 27, 2003, 09:34 PM: Message edited by: clownpuncher ]