In theory, if you take your max rpms and follow that over to what impeller size you have it tells you what h.p. you supposedly have.  I dont think they are the most accurate but more of a ballpark figure.

If you use it to pick an impeller you would have to have an idea of hp and at what range.  Or you might be able to use the chart if you knew your hp and only wanted to top out at a certain rpm, then you might get away with the chart.

Kinda curious as to how many people actually know the hp of thier engines.  I know I sure dont know the exact but I think I have a good ball park figure.

Danger, from the little bit I know, it sounds like you have the correct impeller in your pump but I dont think its a D cut.

This stuff is Greek to me, why do you think it is not a  D impellar,

Also I doubt this ford 460 is only pushin 200 hP !

You can't use the charts to "reverse dyno" the engine.

Truth be told, if you are in fact running a D impeller, then you may well benefit from an upgrade. I'd find it hard to beleive that would be in there with a 460, myself. Your engine is simply stopping at 4800, probably, due to the ignition system (Especially if points or theres an RPM limiter stopping you there), or valve springs, as someone recently showed me. You may well have, Should have, a hundred or a couple hundred more HP there to drive a more aggressive impeller!

The only way to know is to A: have the engine dyno'd, or B: step up the impeller and see what happens!

B is probably cheaper, first, and probably more correct.

I don't know about Jacuzzi's, but every Berk I've ever seen factory attached to ANY big block was an A impeller.

GPS'ing at 50 knots on a D impeller at 4800 rpm, I agree, not reasonable, really. But stranger things have happened I suppose!

Ray

As I already said, confused myself immensely on these charts.

Hypothetically, and REALLY hypothetically speaking  , where does say 900 or so HP at 6000rpm fall onto those charts? (Theres a few of them on here, so not a far reach!).

E impeller? 

Ray

Right off of Berkeley's site.  Might be of help.


To illustrate an impeller choice, a ski boat was run with a C and A impeller. It had 185 hp, V-8 engine which turned the C impeller at 4300 rpm, required 182 hp, with a top speed of 42 mph. It turned the A impeller at 3700 rpm, requiring 162 hp, with a top speed of 40 mph. The loss of 20 hp, due to the lower maximum rpm, only dropped the top boat speed 2 mph. The rpm required for all other boat speeds was 500 less for the A impeller, which lowered the noise level considerably.

But if you think about it, saving the world from noise pollution while running a gas guzzling, air polluting v-8, horsing around for no apparent reason on a lake or river...

Ray

Sssshhhh, one of "them" might hear you.  Then what are we gonna do? 

Probably not very accurate but could "ballpark it"

50 knots = 58mph.  D impeller would be spinning much higher than 4800 to reach that speed.  58mph is pretty respectable in a 21 ft boat and sounds about to par with the results of an "A" cut impeller.

Not 50 knots,
50 MPH of a portable GPS, the boat is a Sleekcraft Executive 23 footer at 1800 pouinds + me and my son = 2200 pounds, this was in a slight chop but no white caps.

Right off of Berkeley's site.  Might be of help.


To illustrate an impeller choice, a ski boat was run with a C and A impeller. It had 185 hp, V-8 engine which turned the C impeller at 4300 rpm, required 182 hp, with a top speed of 42 mph. It turned the A impeller at 3700 rpm, requiring 162 hp, with a top speed of 40 mph. The loss of 20 hp, due to the lower maximum rpm, only dropped the top boat speed 2 mph. The rpm required for all other boat speeds was 500 less for the A impeller, which lowered the noise level considerably.

So you loose HP due to the RPM change, I get it now. But It is hard to believe that this 185 HP motor couldn't turn the A impellar faster. It has 185 HP but is only using 162 HP, Why ? shouldn't it spin the A impellar just as fast ?, That is where I am confused, it is not as if the A impellar has a differeng gear ratio or gear reducer.

Are impellars stamped to see the "cut" ?

Welcome to Socal ! I'll admitt I read down the middle of this thread , First although some relationship exists there are no actual "parrallels" between Jacuzzi and Berks respective to the "RPM" charts This is particularly true of the YJ as it actually operates on a different principle (axial flow vs "mixed flow) However forgetting rpms ,power etc I'm not sure why a boat with a 460 CU motor would have a  "C" Impeller "C"s were typically reserved for small CU motors (Small blocks etc) That said a BBF in an average boat should (will) turn a Jacuzzi YJ "B" typically around 5100 RPMs and a WJ "B" aournd 4800 so.... if you extrapilate that, your BBF (which new/stock made 320 hp) should spin that "C" upward to 5K ,  Assuming your tach is correct I would say your "down on power" and I would be looking at motor , tune up and carburation "issues" Please call if we can help you Tom

re ID of the impellers , the nominal measurements are not in any similar to Berk ,If you have the Impeller out I have some Jacuzzi specs and cut charts (somewhere  )

First although some relationship exists there are no actual "parrallels" between Jacuzzi and Berks respective to the "RPM" charts This is particularly true of the YJ as it actually operates on a different principle (axial flow vs "mixed flow)

Tom, thanks for clearing this up.  I had no idea that berks and jacuzzi operate completely different as you stated.  Goes to prove that you do learn something new everyday!!