SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: soron3842 on September 06, 2011, 04:18:25 PM
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boat is running a 455 olds with berkeley 12jc pump what impeller should be used ??
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Well Im not the most knowledgable person to answer this but from what Ive read, seen and have in my 12jc it would be an aluminum "A" if its under 500 hp.
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ok cool ya i am well under 500 hp i just wasnt sure i am looking at rebuild kits and seen they had all kinds of impellers to choose from so i got confused lol thank you
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I think "A" would be a good call too. :thumbup:
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ok cool ya i am well under 500 hp i just wasnt sure i am looking at rebuild kits and seen they had all kinds of impellers to choose from so i got confused lol thank you
Define well under 500HP. Are you looking for max speed with your rig?
Here's how it breaks down, really. The charts and graphs are so damn confusing, I know. If your Olds is fairly stock, probably in the 300-350 HP range. Hot rodded a little, lets say 400 HP. Now, at what RPM does it hit that? What RPM are you able to hit now and what impeller is in there presently? 4500 RPM is where my mind would be with the Olds, Maximum.
Generally, ALL Berkeley pumps came with A impellers in these boats which is an easy answer even though that is not optimum for your case, or any others, probably. Many reasons for that, but I've owned a few boats that came with STD 460's (320 HP) and an A impeller stock, and a 454 (425 HP) same impeller, stock. I think it's because the manufacturers bought their pumps that way in bulk, and that's what went in everything.
Personally, I would be looking at an AA or a 9.25" if you want max performance from your 455. I doubt your peak HP is over 4500 rpm or so. A larger impeller is going to allow maximum efficiency at lower rpm/peak HP levels. In contrast, a smaller impeller (A, AB, B, BC, or C) is going to allow for higher HP levels and/or higher peak RPM levels to acheive max thrust.
What it comes down to is this. IF your engine is capable of 400 HP at say 5000 or so RPM, then yeah, an A. If it pulls 400 max at say 4500 rpm (Which is where I;d be guessing you are near or at), then an AA. If lower than that, I'd be looking at the 9.25" These are assuming you're after max speed with the power you have available.
Ray
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Thanks rebel that breaks it down alot easier for my simple mind then them damn charts :o ya its a stock 455 olds so an AA impeller would probably be my best bet? I would be happy to get around 50 to 55 mph if that is possible with stock 455? Thanks again :)
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Oh ya its got an A impeller in it now my tach is not reading by sound I would guess its turning 4500 to 5000 rpm more towards the 4500 range tho
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Food for thought....
An "A" or a "AA" can be cut down to a smaller size. A "B" cannot be cut "up" to an "A".
When I had my shop in the late '90's I would always keep an "A" in stock and I would only cut them down if there simply was not enough HP to "pull it"...
Always go with the largest impeller because you can't "put the shit back in the horse".... ;D
You should do fine with an "A" IMHO.
GT
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Here's how it breaks down, really. 4500 RPM is where my mind would be with the Olds, Maximum.
Ray
[/quote]
The important part, X2
Daniel
Mash on it
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Thanks rebel that breaks it down alot easier for my simple mind then them damn charts :o ya its a stock 455 olds so an AA impeller would probably be my best bet? I would be happy to get around 50 to 55 mph if that is possible with stock 455? Thanks again :)
Completely and easily possible with an Olds to hit that. We got back from Big River with my buds/my heavy ass 19' Charger that we just put a fresh YJ pump in, with an Energizer kit, A impeller and diverter (The boat is hitting 5000+ rpm on it's warmed over 455, probably 350HP or so, so if I ever trip across an AA on the cheap I think we're going to replace the A with that just for giggles).
But it ripped off 57MPH, popping from a lean condition (Later found to be a weak fuel pump and I also bumped up the jets a couple steps, timing was a little off), but I haven't been back in it to try my GPS on it again.
I think it might be a mute point to argue the A vs AA until you get an accurate RPM reading of what you're pulling RPM wise REALLY. In my case this is an AT converted Jacuzzi and not a true Berk, even though all the guts, bowl, etc are Berk for all intents and purposes, but your results may be different. Simply put, a fresh rebuild on the pump, new "A" impy may well lower your RPM to the 4000-4500 range, saving wear and tear on your engine and hitting your target speeds. hard to say without a real baseline number and how tired your pump really is. This is just based on my experience with this one , My only Olds, but it has had oiling mods done to it, and a 10qt Dooley pan, windage tray, etc, etc so the high rpms probably won't kill it, but I don't beleive it's making any more power at 5000 RPM than it is at 4500, according to the GPS readings we were getting, and the AA might actually pick up some speed while forcing the RPMs to stay down.
I think you'll probably acheive the same results with either an A or an AA, But as Glenn said, it's easier/cheaper to cut one down than to go and buy another one. ;)
Ray