Reply With QuoteNever mind all that Ranz. Just send that stainless impeller my way. I know just what to do with it.
What impeller did you have in the boat originally? What rpm and speed were you running? Is the motor built up or stock?
A little understanding please on impellers.... I thought all impellers started as an "A" and then they were cut to a "B" or "C". But i see from Berkeley (Click Here) there are A-4, A-3 , and A-2 (AA?) So if understand right a "A-4" will flow more volume of water at a givin RPM than a "A" and a "B" will flow more than a "C". Right??
So if ran a "C" and wanted to lower my RPM but run close to the same top speed i would want to run a "B" or "A" if i have the horsepower.....?? Is there a way to figure if i run X-MPH And X-RPM with a givin impeller, what would a other impeller give?
Does anyone ever run a "C"?
Im getting a headache smile_sp smile_sp Anthony
[ October 06, 2003, 05:42 PM: Message edited by: Ranz1 ]
Never mind all that Ranz. Just send that stainless impeller my way. I know just what to do with it.
What impeller did you have in the boat originally? What rpm and speed were you running? Is the motor built up or stock?
How do you know i just aquared a "AA" Sainless impeller?
A slopy pump with a "A" impeller, Badly adjusted ride plate, a stock 460 out of a 70' Lincoln w/ a Torquer II intake and a HOlley 650cfm carb. It would spin about 4200 or 4300 (i forget)with a GPS of 50 mph.
This winter the jet is being rebult ("Take a Look at my Impeller" thread), I think i got the ride plate adjust figured out, and going to either a 750 or a 800 cfm carb. Eventualy i hope to have a 400+ hp motor.
[ October 07, 2003, 06:29 AM: Message edited by: Ranz1 ]
Ranz1:
A little understanding please on impellers.... I thought all impellers started as an "A" and then they were cut to a "B" or "C". But i see from Berkeley (Click Here) there are A-4, A-3 , and A-2 (AA?) So if understand right a "A-4" will flow more volume of water at a givin RPM than a "A" and a "B" will flow more than a "C". Right
So if ran a "C" and wanted to lower my RPM but run close to the same top speed i would want to run a "B" or "A" if i have the horsepower.....?? Is there a way to figure if i run X-MPH And X-RPM with a givin impeller, what would a other impeller give?
Does anyone ever run a "C"?
Im getting a headache smile_sp smile_sp Anthony
Ranz1,i seen you win that auction on ebay or i think it was you.
Ditto what 565 said Ranz. What can I say..............I'm a jetboat junkie.
Yea it was me, Had to get it
So am i right on the understanding of the impellers?
at a given rpm...a "B" will flow more than a "C". Right??"?Right.
So if ran a "C" and wanted to lower my RPM but run close to the same top speed i would want to run a "B" or "A" if i have the horsepower.....?? Speeds all about power to the impeller. Upsizing will lower rpms, and if you're on a somewhat level part of your engine's power curve, won't hurt speed as much.
Is there a way to figure if i run X-MPH And X-RPM with a givin impeller, what would a other impeller give?Yep. A combination of drag reference point, impeller curves and engine power curve will get you very close to the right answer. With a custom drag curve for your hull even closer.
Does anyone ever run a "C"?Nobody I know. My thought once you cut to C or D you may be taking a significant hit in impeller efficiency and/or launch loading. But no hard data yet to prove one way or other.
jer
Thanks LVjetboy, Just want to make sure im talking the right talk.
But whats up with the A4, A3, & A2? If all impellers start as an "A" are the others a custom cut/make? Who runs a A4?? At what HP sould you consider an A2? Ant
[ October 10, 2003, 10:50 AM: Message edited by: Ranz1 ]
According to Berkeley, the A3 and A4 are for use in "larger boats or barges, and in diesel applications" They told me they don't have impeller charts for them.
At what HP sould you consider an A2? Choosing an A2, or another size depends more on the shape of your engine power curve than any set power level. For example, my engine puts out over 600 true (not corrected) hp at 5700 rpm on a typical lake Mead day, and I'm running a Berk B. If I up-sized to an A2 I'd be significantly short of my engine's power peak, loosing 80 hp and about 5 mph off my top end. Not gonna happen.
So how about downsizing?
My engine's peaked at 6200, but is relatively flat from 5700 to 6200. If I cut to a C I'd only gain about 10 hp from downsizing at the cost of 350 rpm more stress on engine parts and impeller efficiency hit...those extra 10 hp's not worth it.
So to make these choices you need to know the shape of your engine power curve from a dyno, or at least have a good idea of the shape from an engine modeler or past experience. Not knowing that, I suppose if you build an engine with a peak in the low 6's putting out about 1000 hp at 6k, like maybe a blower engine, then the A2's a good choice. Just a guess.
jer
[ October 10, 2003, 01:09 PM: Message edited by: LVjetboy ]
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