hp versus rpm's

[newbie Mike]

Help with my confusion. I am building a Biesemeyer day cruiser 24'4" on OAL. Jacuzzi 12 WJ with an aluminum impeller. I do not have a impeller selection chart for the Jacuzzi but the local Jet Guru says that the WJ impeller performs like the Berkeley A impeller. My 460 Ford dyno'd out @ 390 hp and maxed out at 396 pounds of torque @ just less than 4800 RPM the Berkeley impeller chart says that with an A impeller and 350 hp 4800 RPM is Ideal, however at 400 hp 5050 RPM is ideal. So do you guys think it adviseable to try to get more RPM's out of my engine? Further it states Aluminum impeller not recommended above 325 hp. I'm concernec :confused:

[quiet riot]

Newbie, I think you'll want as much pull outta the hole as you can get with a 24ft jet. I've found my A imp pulls better than my B. Its a legend pump and I've put around 600 hp to the al imp's. 4-500 hp seems to be a safe range I can come outta the water and load/unload the pump and still have no issues with aluminum on my pump.
The only problem I had was when trying droops and wedges which caused a cavitation outta the hole and I grenaded an al imp that way. Before that I ran al imp's for 7 years, even through rapids and sucking rocks without any prob's.
Maybe a wj owner can chime in and give you some exp they have. Unless your planning a high rpm, high hp engine (6k rpm, 600+ hp) I think you'll be much better off with an A or AA.
jd

[LVjetboy]

A Jacuzzi WJ A is very close in hp to a Berkeley A according to mfg charts. Also, as far as I know, the WJ does not come larger than A.
When you quote dyno numbers understand that corrected and measured are two different things. Impeller charts are keyed to actual power required to turn the impeller at that rpm. Has nothing to do with "ideal" or corrected. Only has to do with power required to turn the impeller at that rpm. When you run at the lake, conditions are most likely different than dyno measured and surely different than dyno corrected. So take that into consideration.
The answer to your question depends on what rpms and conditions you run at. For top speed you want to match peak power, not peak torque. If your engine's peak power is at 4800 and you're way way short of that, then you may gain top speed with a cut. But there's a tradeoff in power gain vs rpm increase. And for a 24' cruiser, you'd need a significant gain in power to see any change in speed and make that cut worth it. My guess is a cut won't pay-off for your engine and hull size.
BTW, pump charts are in a free program called the JPC, email me if you want it.
jer

[1HOTGMCJET]

NewbieMike, the Jet Boat Performance calculator (JPC) is a GREAT tool - be sure to take Jer up on his offer.....by the way, LV - if no one else has said it, I will - THANK YOU for sharing the JPC with all of us! :)

[1975sleekcraft]

A Jacuzzi WJ A is very close in hp to a Berkeley A according to mfg charts. Also, as far as I know, the WJ does not come larger than A.
When you quote dyno numbers understand that corrected and measured are two different things. Impeller charts are keyed to actual power required to turn the impeller at that rpm. Has nothing to do with "ideal" or corrected. Only has to do with power required to turn the impeller at that rpm. When you run at the lake, conditions are most likely different than dyno measured and surely different than dyno corrected. So take that into consideration.
The answer to your question depends on what rpms and conditions you run at. For top speed you want to match peak power, not peak torque. If your engine's peak power is at 4800 and you're way way short of that, then you may gain top speed with a cut. But there's a tradeoff in power gain vs rpm increase. And for a 24' cruiser, you'd need a significant gain in power to see any change in speed and make that cut worth it. My guess is a cut won't pay-off for your engine and hull size.
BTW, pump charts are in a free program called the JPC, email me if you want it.
jer
i know this is an old thread but i'm wondering!!!!!!!!!!!!!!!!
ive done some research on jacuzzi--correct me if i am wrong--
jacuzzi-dosent-make-an--A--impeller
the onle site(don't remember now)i found that showed replacement impellers--B--C--D--E--and if i remember correctly--F--
now i have a--B--in mine.
been told if i have a B impeller-------through it away--------!
been told B impellers are the way to go--jacuzzi only--!
can anyone shed any light(or facts)on jacuzzi impellering!!!!!!!!!!!!

[malcolm]

The guys who own Jacuzzi, North American Marine Jet, list A thru D in their parts list. It seems like 95% of WJs came with Bs.

[napabob]

nM,
There is also some machining you can do to the bowl if you have a Place diverter.
Jim Brock
Cyclone Speed & Marine
(818) 890-1867
Jim Coffey
Performace Jet
(707) 823-6713
http://www.hotboatpics.com/pics/data/500/6782JacuzziBowl-Model.jpg

[1975sleekcraft]

The guys who own Jacuzzi, North American Marine Jet, list A thru D in their parts list. It seems like 95% of WJs came with Bs.
i thought i had been to that site before--i tried northamericanmarine.com--wasn't the one--
can someone point me in the right direction------THANX---------

[396_WAYS_TO_SPIT]

The guys who own Jacuzzi, North American Marine Jet, list A thru D in their parts list. It seems like 95% of WJs came with Bs.
Which is similar to a berkley "A"

[Floored]

B jacuzzi is same as berk A Jacuzzi A is berk AA Jacuzzi A is available.