Impellor Help Please

[Rooster]

Ok I had a zz502 engine that was a little tired that blew on me but I was running about 60 on a AB impellor at 5000rpm. I just installed a new engine that dynoed in at 685HP and 715torque but with the same impellor setup, but it is dogging out. I cant get it above 4400 rpm and over 50 mph...
Im not reaching my power band on this motor, what impellor whould I be running??? Redline on the motor is about 7000 per the engine builder. Any suggestions???
Ohh and the boat is a heavy 21' open bow 79 (Solid wood)

[BrendellaJet]

Need to lower the motors power band. I wouldn't cut the impeller.

[cook1]

It would take about 500 ft/lb of torque to turn your impeller at 5000 so you got to have more than that to make any more rpm. If your making 685 at 7000 rpm thats only 513 ft/lb. It probably makes more torque a little lower but buy 5000 it may be below the 500 ft/lb mark. Like the man said you need to bring the peak hp or torque down or just cut the impeller and let buck!

[BUSBY]

What RPM was that 685 & 718 at ... I wouldn't hesitate in making fine cuts in your impeller until you reach your desired RPM ... just keep in mind that if you cut it back too much, you can't go back.
I sent mine (A cut) to Tom Papp 4 times until it was dialed into 7900 to 8200 rpm's ... then it was running the number all of the time.
Good luck!

[Rooster]

Thanks!!
I think I am going to try a B impeller to start, then go from there. Or should I get an A and get it cut? I think I have a bronze A right now.

[SmokinLowriderSS]

It looks like you may have a cam & intake setup in that motor that is optomized for high RPM. I'm running a 454 set up to only 400 HP at 5,000 and carries 468lb-ft torque to 4400RPM and I am having no trouble spinning a berk A at 4700 and running 60MPH in my old Taylor SS. You get 2 choices because the drive doesn't care, adjust the engine to bring the muscle of that 502 down lower to spin the jet harder or cut the impeller (or buy a smaller one) to let your motor rev more and spin it harder at a higher rpm.

[Squirtcha?]

My guess is going to a smaller cut impeller you're gonna get a lot of slip out of the hole, and have trouble moving that 21 feet of lumber. (did you really say it was solid wood?)
Bigger boats usually like the bigger cuts (A or AA etc.)

[SmokinLowriderSS]

with Squirtcha. You need to run an A (in my opinion) to get decent acceleration / holeshot with a 21 footer. IMO, your best bet would be to (now that your engine is built) re/de-tune it to bring the HP curve to a lower RPM without sacraficing any more HP & Torque than you have to. Too bad you didn't (it seems to me) build the motor to throw a jet arround in the first place. Hi-reving car motors are great but they don't work real well in jets, especially larger, heavier jets.

[eliminatya]

if that is an aggressor bronze A cut it down to a B, that impeller is like a berk AA, i have an aggresor A with aprox 1000hp and only spin 6300.

[SmokinLowriderSS]

From what I have heard, if his agressor A is cut to a B, that leaves him basically my Berk A, which I am having no trouble spinning 4700 and still fine-tuning carb setup testing. Looking at 5,000+ with the extra 150 of N2O on it. His early post said an agressor AB, which still leaves him a bit bigger than My A but he is still unable to spin it worth a darn with that engine setup as it is.

[Aduner2]

My guess is going to a smaller cut impeller you're gonna get a lot of slip out of the hole, and have trouble moving that 21 feet of lumber. (did you really say it was solid wood?)
Bigger boats usually like the bigger cuts (A or AA etc.)
I second what Squirtcha said. Fuel consumption and motor spinning that many rpms would drive me nuts. Inducer might help the hole shot thou. Figure 300 to 400 rpm increase dropping impeller size from A to B. Hard part is figuring out where the motor power band is without r&r-ing the impeller a few times to find it.

[Bense468]

Different Cam to bring Curves down to lower RPM range. What kind of heads?It is hard to tell without a dyno pull what you got. However I would not run that small of an impeller with that big of boat. Your going to come out of the hole hard with an Berk style AA or aggressor A (about the same)and fuel consumption would be the best if the motor is setup right for it.

[SmokinLowriderSS]

Unfortunately I also gotta agree with soem of what LVjetboy said. sems to be a lot of shotgunning goes on in most posts, due mostly I believe to partial info. Below is a copy of what my engine setup come to on Desktop Dyno. No, I do not have dyno shop numbers as my budget is unavailable for such things. What it claims is pretty close to what Berk's charts demand too.
RPM HP Torque
2000 175 460
2500 222 466
3000 265 464
3500 312 468
4000 354 465
4500 387 451
5000 403 423
5500 397 379
6000 371 324
I have no clue about my redline but I figure 6,000 would be close. I been running a lot of CAST parts inthis motor 27 years (pistons & crank) and feding it nitrous at 5300 for most of that time. SHe's been fast and reliable as a brick.
As said before, I'm able to spin a Berk A to 4700 and have gps's that in my old, rough-bottomed Taylor SS to 58MPH. Don't know where my 150HP N2O takes me to yet. With a set of info like above Rooster, I think we could be of a lot more inteligent and direct assistance.

[Rooster]

To clairify the pump is a Berkeley JC. I bought the boat used so I havent been in the pump yet but Im taking it out this weekend for a rebuild and to make sure what Impeller I have.
THe boat isnt really solid wood but it is a heavier boat 1979. When I am at the top RPM's it feels like it is just about to break out but cant quite get over the hump...
Unfortunatly its looking like Im going to have to make the engine builder change out the cams. I pulled out the cam card yesturday and almost fell over when I saw .629 Lift, .015 Durration 306, .50 Dur 260, Lobe Sep 110. With 2.3 and 2 valves on ported dart heads. 11:1 Comp....
I will find out where I really am at this weekend and get the Dyno sheet for the engine...

[SmokinLowriderSS]

You ARE working a hi-RPM cam. WHEW! I'm only running .565 lift on a duration of 280 deg. 110 Deg lobe centers. 2.05"x1.90" valves on large oval port iron heads (open chambers) 8.5:1 compression.

[SmokinLowriderSS]

Just advancing the cam 4 degrees or so might lower the RPM range of your motor enough to help it pull, unles you are already running advanced on the cam. I just tried to load your motor into DESKTOP DYNO to see what it shows. How big a carb you pouring fuel through? To get your HP figures I had to go to 1,000 CFM and don't show your HP fig. If desktop dyno is even close you are peaking out at 6,000 RPM for 684HP & 665 lbft of Q at 5,000RPM. Looks like a good strong motor, may just be a touch behind the pump for building it. That is why I think if you are running a straight up cam, degree it 4 deg first and retry (as long as all those moving pieces clear). :clover: :clover: Good luck.

[Rooster]

Here is what I know for the Desktop dyno,
Its a 496 Gen IV block
Lift and durration stated above
850 Mighty demon carb
Victor Highrise intake
Internally balanced 11:1 comp
Im going to try and bump tbe advance
and change to a B impeller and just be happy...
But I am curious what you desktop dyno comes up with...
Thanks all for your help, Everyone!
P.S. Anyone know where in OC to get an impeller replaced for a reasonable price, or is it something that isnt too hard to do "Properly" Myself?

[SmokinLowriderSS]

Any head info? Ports large oval, rectangular, any porting work done or basically stock?
And whatcha running for exhaust?

[Rooster]

2.3 and 2 on the valves. Rectangular ports (Huge) CNC Machined and ported. Matched to intake. Exhaust is the bad part, they are manifolds that have been ported lightly. Didnt want to risk entering the water jackets (Need somemore money for lightnings)
Dart 119cc Chamber
350 Intake runner
200 exhaust
Hope that helps. I am curious what the desktop dyno says.. Thanks you! :)

[SmokinLowriderSS]

I just realized that I was running your cam specs at a seat to seat measure, not at a .050" lift measure. changed that and the curves changed RADICALLY! Unfortunately, they moved toward higher RPM's.
I have the older free version available on the web so some of my options are a bit limited. I ran your hi-rise manifild as a tunnel ram since it was a hi-rise instead of a single plane.
I generated this with ported oval-port heads and large-tube headers. Rectangular ports (ported) make more HP but it is all higher, above 5500RPM. More torque to but again, 98% or it above 4,000 RPM.
RPM HP Torque
2500 168 352
3000 221 387
3500 278 418
4000 346 454
4500 426 496
5000 502 528
5500 564 539
6000 609 533
6500 633 512
7000 643 482
With rectangular heads you HP peaks at 752 @7500 RPM. Torque peaks at 588 from 5500 to 6000 RPM
4,000 368HP 483Tq
4500 455HP 531Tq

[SmokinLowriderSS]

The rrevised figures for your heads. :frown: Also had to run "small tube headers, open exhaust" to try to match for the logs.
RPM HP Torque
2500 180 378
3000 236 414
3500 301 451
4000 377 494
4500 463 540
5000 545 572
5500 611 583
6000 660 577
6500 691 558
7000 709 532
7500 714 500

[SmokinLowriderSS]

The way that cam is set up, you are running less muscle than my mild 454 all the way to 4,000RPM. Problem is you'r behind the pump's pull so it prevents you from getting the engine's muscle.

[bp]

P.S. Anyone know where in OC to get an impeller replaced for a reasonable price, or is it something that isnt too hard to do "Properly" Myself?
OC, as in orange county, ca?

[Oldsquirt]

OC, as in orange county, ca?
Bet you're thinking what I'm thinking, Bob. :D And he could probably walk a few steps and get a cam recommendation while he was down there.

[Rooster]

Thanks oldsquirt.. I will call him today. Maybe tow the whole son-biatch down there since it is in my warehouse in Santa Ana off Dyer...
I think I have a better grasp on whats going on now... The question is can I fix it with a cam? OR will it be more serious :(

[cook1]

There is a problem with just changing out the cam and still having the large ports in your heads. The intake charge velocity will fall and this will limit the amount of torque than you can make at the lower rpm. You might be able to get some port fillers like what is available for some of the Ford factory heads that have large ports.

[Rooster]

Found out that the impeller was an agressor Bronze A... So according to Oldsquirt thats a Berkeley AA.

[Oldsquirt]

I didn't read Oldsquirt's post in this thread saying that. But if you prefer to quote him as authority fine.
Nice attitude, sparky. :rolleyes:
Jer, it was in a different thread on another board. He posted a pic of the impeller, which led me to suspect Aggressor. Side by side comparison of the leading edges, as well as the fact that is was stamped "A", seems to confirm that. A quick glance at the Berkeley impeller charts, and knowing what engine he had in the boat previously, didn't hurt, either.
By the way, I DO NOT consider myself any kind of authority. There's only a small number of those across this country. All I try to do is help people out with some basic info when they need it.

[Rooster]

Hey... LV
Im just trying to figure out what I need to do here and Oldsquirt was just giving me advice, which is welcomed! Im learning and the only way to do that is to ask questions and compare answers. Plus I called agressor and they confirmed that a A Agressor Bronze does = a berk AA

[Her454]

Nice attitude, sparky. :rolleyes:
By the way, I DO NOT consider myself any kind of authority.
ROTFLMAO...............Well I damn sure do........... :D

[SmokinLowriderSS]

I consider myself an authority ....................... on my opinion,....... which has been proved to be in error once or twice. :jawdrop:

[SoggyJet]

2...... Exhaust is the bad part, they are manifolds that have been ported lightly. Didnt want to risk entering the water jackets (Need somemore money for lightnings)
In my humble opinion you need to uncork that exhaust. You have huge valves, big cam but stop it all up trying to get through the exhaust manifolds. You did not say specifically, but I assume you mean these are "logs". Logs can kill serious horsepower. Even standard Merc type center riser manifolds are better than logs. Just a thought...if you get back the horsepower lost in that exhaust you may not need a smaller impeller or smaller cam.
Doug McCoy

[FHI-prez]

I agree with Soggy. You can throw all kinds of numbers in desktop dyno and never get an idea of what to do. The high rise manifold is for high rpm power, the cam is a bit stiff for what you are trying to do, and the manifolds are absolutely killing you! You get NO scavenging from manifolds, which that cam needs. You need a jet boat friendly cam, probably a dual plane intake (arguable at best), and good exhaust and that thing will run like a rabid dog. Cutting down the impeller is a band aid on a bullet wound in my worthless opinion. I'd say your biggest liability from what info is known is your exhaust, especially if you have logs. You can lose horsepower with big cams, big heads, big valves, high intakes...and try to blow it all through exhaust that is more restrictive than what came on a '74 460 station wagon. Only one small snag, if you gotta use water jacketed thru transom headers, hold on to your wallet! If your boat will be so kind to let you use water injected OT headers, you can stay well under a grand. Marine exhaust ain't cheep! :skull: :yuk:
Nick

[Rooster]

They are aluminum risers... That have been ported a little but there isnt much room in there before you get through to the jackets and probably worse there are gibson 496 muffler tips on there too (Which werent there before)... Its a little better than logs but not much... Honestly Im going to invest in some headers as soon as my wallet permits... But 4k for exhaust seems nuts...
Well I had a Agressor A Bronze impeller, just finnished installing a AB American Turbine with an inducer, and ride plate... And I am off to the river to see how it all works out!
Either way, thank you for all of your help! And wish me luck

[bp]

By the way, I DO NOT consider myself any kind of authority. There's only a small number of those across this country. All I try to do is help people out with some basic info when they need it.
yer doin a fine job, keep up the good work. :cool:
whatz an authority :confused aren't we still on the internet? kinda like hollywood and actors; everybodyr1... :D

[SmokinLowriderSS]

http://www.cpperformance.com/products/Exhaust/lightning-headers.htm
Lightning headers (I want some this winter). $1700 a set
Half the price of some others and I have heard really good things about them. :cool:

[LVjetboy]

"Hey... LV Im just trying to figure out what I need to do here and Oldsquirt was just giving me advice, which is welcomed! Im learning and the only way to do that is to ask questions and compare answers. Plus I called agressor and they confirmed that a A Agressor Bronze does = a berk AA"
You welcome Oldsquirts advice. From what I've read his advice is solid. BTW, the answer to your question (Aggressor A = Berkeley AA) already programmed into JPC. Done deal. You want impeller cut advice? Before you called Aggressor or talked to Oldsquirt, I talked to Aggressor and got their pump curves back in 2002. Dave told me Aggressor A equals Berkeley AA, that the best info I could get...some things don't change. Guess what JPC is free, always has been always will be.
"By the way, I DO NOT consider myself any kind of authority. There's only a small number of those across this country. All I try to do is help people out with some basic info when they need it."
Ya whatever. I'm no pro either. Don't consider myself a freakin' authority on anything... just post my opinon and experience. Take it for what it's worth. I could care less about funny or image. Pump curves not basic info? Maybe they should be.
jer