Which Impeller

[jimsride]

I'm new to this board, give me a little love guys. I asked earlier about impellers, I have 18ft Biesemeyerw/legend jet, mild BBC gen6, hotter chev roller cam, headers, performer and holley 750. It runs about 5500 rpm now, I have an AB impeller. I like acceleration, not necesarily top speed. LVJetboy sounds like he knows what hge is talking about, I just didn't quite follow.

[flat broke]

Relatively easy to answer question. Take your dyno sheet and overlay it onto the impeller charts found at http://www.liquidaddiction.net/impeller.html and grab the biggest impeller you can that doesn't intersect too far down on your RPM from your dyno sheet. Basically if you like leaving harder than having top speed numbers move to a larger impeller than what you have. Not knowing what you specifically want out of the boat makes it harder to answer the question. Since I think LV even had an 18' Biesemeyer at one point in time, he might remember what he was running and how it worked.
Good luck,
Chris

[Bense468]

I have an 18' Biesemeyer and I am running a AA it comes out real hard. Spinning 5100 looking for 5500 when the motor goes back together. We will see.
[This message has been edited by Bense468 (edited June 03, 2002).]

[HBjet]

Originally posted by Bense468:
I have an 18' Biesemeyer and I am running a AA it comes out real hard. Spinning 5100 looking for 5500 when the motor goes back together. We will see.
Bense, what power are you running again? Because an AA for a 18' boat you would need some serious power to spin it at 5100 RPM. I have a 19' boat, no serious power, and I'm spinning a B at 5100-5200 RPM. When was your last pump rebuild?
HBjet

[wrightnow]

HBjet, Is 5100-5200 rpm an improvement from last year?

[HBjet]

Originally posted by wrightnow:
HBjet, Is 5100-5200 rpm an improvement from last year?
Well, last year I was around 5000-5100, but I also realized this last trip out, my RPM guage is acting funny, I don't think it's very accurate.
HBjet

[77charger]

5500 for an a-b sounds a little high unless you have some good power.If the pump is tight then you have good power and a, b cut will only run a little higher and maybe a litlle gain.Hb jet you have to remember with the blueprinting your rpm will be lower than without it so your rpm could be right.shit mine lost 400 from bowl and a complete impeller detail same speed though.

[INFINITEJJ]

Originally posted by HBjet:
Well, last year I was around 5000-5100, but I also realized this last trip out, my RPM guage is acting funny, I don't think it's very accurate.
HBjet
Must be going around, just rebuilt my motor over the winter to a "no serious power" 460. Now I am turning a Berkley "B" to 5100 from 4600 RPM, My guage is acting a little funny also, maybe it doesn't like change? Gonna have to check it out.
JON

[froggystyle]

You guys better define "good power" because I am spinning an "A" at 5500 with a medium motor build.

[flat broke]

Froggy,
You've gotta be turning around 625hp with your mill. Now consider 625 from say a NA 460 or 454, would you not call that good power? Everything is relative. For the bigger CI mills 625 is an okay number or even a starting point for the guys with the 540s. For those of us with less than 500 CI, 600+ is good power for the level of cash and work most of us have in our mills. The reality of the situation is that the "average" jet boat probably has around 400-425hp. So once again 600hp would be a big improvement. Don't take this negatively. Your boat does the exact same things I want mine to do when I'm done with it(minus the stereo then add about 7 mph http://free.***boat.net/ubb/smile.gif ) But since I'm one of the small cube guys I figgured I'd chime in with my take on it. In my mind, a 454/460 making an honest 600hp below 5500 consitutes good power. That 600 HP in a decent 18' shallow v hull is going to be worth 70-low 80s with decent setup. Once again that is far above the average for jetboats as a whole and would be considered good performance. Not the fastest kid on the block, but you also didn't spend 20k on a motor. Once again, I'm not dissing anyone, just giving my take one the definition of "good" power relative to recreational jetboats.
Chris