What king of RPM and HP difference will I get switching from an A to an AA? I am trying to lower my RPMs without losing any top end MPH (a gain would be nice too). How much a difference does it really make? Current set up is a 425 HP 454. Engine is still new so my rev limiter is set at 5000. Feels like it wants to climb higher and feels like there is little if any water resistance.
What condition is the pump in? Is it brand new? I would say you stick with the A and I'm guessing your pump should be rebuilt. That will lower your RPM's by 400-500 and should give you a few extra MPH.
HBjet
Another question, what boat is this in? If it's a 22ft daycrusier, I wouls say the AA would be the impeller to run, if it's a 19-20 boat, stick with the A.
HBjet
[This message has been edited by HBjet (edited April 23, 2002).]
Pump is in good shape I believe, but am starting to question it. It was rebuilt a year ago and I just did some work to the intake, ground off some sort of casting seam. The boat is a 2001 Ultra 21 LX. Everyone tells me it should easily go 65 but at what RPM? I do not want to rebuild the motor every year because it runs at high RPMs on a regular basis. I built the boat from a bare hull. http://free.***boat.net/cgi-bin/imag...l&tt=&bool=and
Nice boat. I think 65mph on a stock 454 is a little stretched. I would say in the upper 50's for that hull. There are a lot of different things you can do. If you don't already have one, get a Plave Diverter. This will help you trim the boat, getting more of the boat out of the water, freeing it up. You can also play with intake grate and shoe setups. Once your loading the impeller properly, you can start playing with the motor if you still want more.
HBjet
IMO - To go 65 in a heavy weight forward daycruiser is going to take a bit more than 425hp. You probably need more like 500hp and an AB impeller.
What brand of impeller do you have. I have a 400hp 454 and an American Turbine A impeller. My motor turns it 4,600-4,700rpm. If your turns it 5,000+ rpm you either have more horsepower than you think, a loose pump, or a smaller impeller.
I did put a loader grate in it and it seemed like it did make some water resistance in the pedal which made me think an AA impeller was the right direction to go. The motor is not bone stock, it has JE pistons, Manley valves, Milidon 10 qt. pan, GM Perfomance cam from a 502, GM performance valve springs, and the lower end is balanced. It is a copy of a GM 425HP crate motor. Don't you have to pull the intake out of the bottom of the boat for a shoe? That sounds like a mess. There has got to be an easier way.
Actually for a ride plate and shoe, you have to pull the motor and intake. The intake then has to be machined for the shoe/rideplate, and reinstalled.
Originally posted by BowTie Rick:
I did put a loader grate in it and it seemed like it did make some water resistance in the pedal which made me think an AA impeller was the right direction to go. The motor is not bone stock, it has JE pistons, Manley valves, Milidon 10 qt. pan, GM Perfomance cam from a 502, GM performance valve springs, and the lower end is balanced. It is a copy of a GM 425HP crate motor. Don't you have to pull the intake out of the bottom of the boat for a shoe? That sounds like a mess. There has got to be an easier way.
BTR, I sense that you're more concerned with longevity,than a couple of mph gain.I would check what cam you have ,and go for a bit more lift.Then install a "AA" impeller.With 450-475 HP on tap ,you should be able to maintain 60-63 MPH with your boat's design.I would also recommend the hydraulic place diverter setup,to get you on plane with some hefty friends aboard. http://free.***boat.net/ubb/biggrin.gif BTW,nice ride you have.
[This message has been edited by spectras only (edited April 23, 2002).]
BTW, the difference in RPM between a AA to an A would be about 300rpm. However its also dependant on your peak HP/Torque curve.
OK, I am getting the jist. I do want longevity but also want more speed. I know it is a fine line to walk but with proper planning it should be obtainable. I do have a jet-o-vator now, would a place diverter really make that much difference in planeing and speed?
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