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Thread: Ok... HERE'S the real reason...

  1. #1
    ...that I'm trying to understand the ratio of pump RPM/suction/nozzle whatever to speed..
    My friend and I have the same boat. 20.5 Elim sport cruiser. Mine is factory orig (WITH water in the @#% damned oil...) His on the other hand:
    Bare hull, no interior whatsoever, no carpet, no side panels, nothing. No deck hardware. Two bucket seats only. We checked the bottom with a 4 foot straight edge. the bottom is still straight. (It had been straightened when it was painted 3 years ago)
    The engine: 488 inch Ford, Major head work, Steel rods, big ass roller cam (sorry, don't know the specs) MSD ign, 10-71 Mooneyham, 2 Barry Grant 850's, Rewarder headers. SUPPOSED to be about 850 hp. It makes 12 lbs of boost. Cost $25,000
    The Pump: Berk JC with a loader and Place Div. the impeller is a Berk SS AA. The pump is unmodified.
    We live at 4500 feet elev.
    My boat, 4600 RPM, 55mph.
    His boat, 6500 RPM, 74mph.
    He thought that with that much engine he could hit 90. He is soo disappointed in the boats performance that after 4 outings this year, he has parked it. I know that you guys are going to jump up and down and say, "The Pump... MPD the pump"...but do you really think there is that much performance to be gained there?
    He spent a shit load of money on the motor, and he is really unhappy with the results, so he is very reluctant to spend another 3 grand on the pump.
    The way he feels right now.....
    "Eliminator for sale...big ass motor... kinda slow...$15,000.00"
    I've been trying to convince him to spend a little more on it and keep it. Help.

  2. #2
    HEY DUDE!!!!! I LEFT YA A MESAAGE on your last post...Now that you gave up some particulars I can help ya...I see several problems already. You want me to tell ya here or over the phone?

  3. #3
    Your spelling is pretty good...lets have it here, so that everyone can learn from my buddy's choice of mods.

  4. #4
    If its an unmodified berk, there is major mph to be gained by spending the $$$. Most stock boats pickup 3-6 mph bluebrinting a older berk.

  5. #5
    the pump*********the pump*********the pump
    don't know the hull but if your spinning 6500 rmp and going 74mph that thing is either made out of cement or the pump needs to be worked. LV has charts for rpm, mph, and some hulls so if you ask he might give you an idea of mph for hp and hull design.

  6. #6
    Yes I agree... the pump the pump
    I have a 509 850hp Spinning a MPD race prepped SS A impeller 6000 rpms and i an running 94 mph. I have dialed out most of my hop and now playing with shoe deapth so add more speed. I should be in to 100's by next summer but up here in Chicago it is no been in the 50's it gets really cold at 90mph at that temp. it's always nice to have the tears freaze to your face as you make a wot pass in the cold weather.

  7. #7
    Ok..first off.My names Rob. I build racing engines for a living. Some of my customers are past and current Promod racers in NHRA/IHRA as well as alot of offshore racing teams.
    Just by looking at your latest post and not seeing these things first hand, heres where I think your problems are.
    The eliminator hull your using is more of a daycruiser than a raceboat. IT'S HEAVY. I personnaly wouldn't waste my time or money trying to get that boat to anything more than about mid to high 70's or so. Forget seeing 80's let alone 90's with that boat.
    As far as the engine is concerned, I build more GM based (merlin, rodeck, kieth black) type engines but fords are great torquey engines. The one thing that pops out at me is that your running A 10:71 MOONEYHAM BLOWER @ 12 POUNDS OF BOOST MAKING APPROX. 850HP. If it really is a 10:71 running 12 pounds than it should be making alot more horsepower than that. Thats a lot of boost with a big blower. Those are typically numbers you would see using an 8:71. A 10:71 @ 12 pounds of TRUE boost will make ALOT more than 850 hp. Are you running a superchiller with this? Especially in that thin air. Thats a big blower NOT to be. Were are you measuring the boost from? Sometimes on smaller motors with larger blower such as yours, boost can backup into the intake manifold and when that happens it shows up on the boost gauge as boost. However, its not a TRUE boost. Anyway, the motor sounds pretty stout but double check that blower size.
    Another thing I see is that your using a JC pump. Berkley made this pump as a cheap (INEXPENSIVE) pump for mass produced HEAVY boats. It is designed to move alot of water at a very low rpm. It becomes its worst enemy at anything more than about 4000 rpm. It simply can't move the volume of water. I would like to see ya run a blue printed JG pump with an A impeller and a stuffer since heavy boats tend to cavitate without it. Are you running a shoe and plate? If not you need one. Since that thing is such a heavy boat, I would imagine that your still running ALOT of wetted surface as well. I would be able to tell if you had a picture of it on plane. I wanna see how much boat is in the water. Those ar just a few things that pop out at me. Hope it helps. I will be glad to give you my shop number if you wanted to discuss it furthur.

  8. #8
    That hull sounds alot like the one my bro had. His was a 82 Eliminator closed bow V hull inclosed motor w/ the jump seats on both sides of the motor cover. It had a Hardin Marine BBC (330 h/p I think) w/ a Berkley. If it is the same thing I personally dont think there is alot you can do with it. That thing was a PIG. Dont get me wrong, it was one of the nicest riding small boats I have been in but it was soooo heavy. I was told his was a 20.5 Sport Cruiser but it didnt say Sport Cruiser anywhere on it. His was White w/ browns and tans and had wood grain looking stuff on the bow in front of the windshield. Yours might not be the same type of hull so dont hold this against me http://free.*** .
    [This message has been edited by fryzll (edited September 27, 2001).]

  9. #9
    Oh ya....One more thing..condesation is pretty common in jetboats. A few reasons why are 1) Your oil isn't getting a chance to get to it's PROPER operating temp. and that helps create codensation buildup and THAT inturn creates a tiny bit of contamination in the oil. Another reason why jets are so hard on unproperly built motors is that tend to blow headgaskets. Water shows up in a cylinder or on a plug check and most people feel like the motor is going bad. Whats most likely happening is this. Jetpumps feed a tremendous amount of water preasure and that water preasure sometimes can blow past head gaskets and into cylinders. If it does it enough than you hydraulic a piston and the party is over. Your engine,as are most head gaskets, designed to withstand certain water preasures. Something along the lines of 12-15 psi. A jet pump can feed it well over 300psi. I have cured this problem 2 ways with my engines. 1)I O-ring my engines and I install a water preasure valve on the intake side of the pump. I set it @ 15 psi and leave it alone. Haven't blown a head gasket due to this problem in 3 years.
    Your condensation can be cured by simply letting the motor build some heat.

  10. #10
    What Water regulator do you use? Do you sell them?

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