Help with Boat attitude/rpm
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Help with Boat attitude/rpm

  1. #1
    Senior Member Double A's Avatar
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    Default Help with Boat attitude/rpm

    18' 1977 Tahiti Super Tiger Bubble Jet

    So I bought this boat in poor shape. Put my first paint job ever on it. Did the Upholstery myself and built this Engine with My Dad. As he knows more than I in most departments.

    SO here is the dilema... Its got a Panther and its glued to the water as well. Very poor lift.
    Any one have some performance knowledge on these?

    Its blueprinted and balanced and only a half dozen rides on it. Supposedly good for 450 hp...I think not. Not in its state of tune that is.

    The boat goes a little over 60. Its about 450hp and runs actually quite well up to 5500 rpm then from there to 6000 rpm it seems to be cavitating or running out of water...not bad just seems excessive on the rpm vs mph gain above 5500. I'm no expert on jets by any means. Just doing this for fun/project but want a little more speed.

    So heres what we did this week. We reworked the bottom of the boat, taking nearly a 1/4" hook out of it. (Should've done this first but I was more interested in getting it running). Going to speed coat it with lubribond. Next we took a look at panthers version of a jetovator. It is very short. Most of the water just sprays right through. Some gets deflected upward. Not enough for good lift of the bow.
    So we are making the jetovator twice as long. Not adding any more degree up just length to apply more force to lift the bow. Sort of a tune up is all..
    not exactly what we wanted to do...but a compromise. It is also now operated by a place diverter hydraulic pump/cylinder instead of the crappy, non locking handle panther gives you.

    My question is How do I load this pump better at speed? It doesnt really seem
    to have any shoe on it. Just a ride plate with a big fat lip in front of it thats about an inch thick and rounds upward to the intake approach angle for lack of better term. Any ideas on how to better load this pump at higher rpm. What can I do? I can make or have just about anything made. I just need and idea of what may help keep the pump more efficient at speed.

    I know I'm not going to go 80 mph. Thats not my goal. I wish it was, but not with this boat... Just a little more would be good. Isnt that always the case?

    Forgive my lack of jet pump terms/description as again I am no expert.

    I am aware of the energizer kit etc. But no $ for this now. Next time we will get that part right.


    I can get a good picture of the intake tract, rock grate, and ride plate
    if that would help some of you that havent seen one or need a refresh.

    I would surely welcome any advice.
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    Last edited by Double A; 08-14-2010 at 01:28 AM.

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    Senior Member jetboatperformance's Avatar
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    We've been working on "hardware" and options for these since the Energizer , but still not finished , maybe this winter Found an obscure patent some time back where a device had been developed to actually open/close down the intake area at varying speeds and conditions This was apparently concieved by/for Early Maritec (Panther) was I belive was a pre cursor to the current Panther Tom

    some pretty "heady" stuff but an interesting read nonethe less:
    http://www.boliven.com/patent/US4449...poration%22%29

    Abstract
    A hydrojet boat drive for efficient transition from low to high speed boat operation, characterized by a conventional drive pump unit and prime mover installation in the "slot" of a "V" bottomed hull and featuring a low drag ram-scoop with a blow-in door or panel which is responsive to imbalance between internal flow pressure and external slipstream pressure, whereby intake volume is augmented for low speed operation and ram pressures contained for high speed operation.


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    Senior Member Double A's Avatar
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    This is very interesting. Gonna have to eat some breakfast then I will check that read out further. Guess I have to register in boliven to see completely.

    Oh, and by the way. I bought the Hydraulic pump/ cylinder for the jetovator from you and a nice steering wheel. You guys got it right out to me the same work week and it went right in the boat along with the engine install.

    Worked out really well for me.

    Thank you for that and your helpful reply.

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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by Double A View Post
    This is very interesting. Gonna have to eat some breakfast then I will check that read out further. Guess I have to register in boliven to see completely.

    Oh, and by the way. I bought the Hydraulic pump/ cylinder for the jetovator from you and a nice steering wheel. You guys got it right out to me the same work week and it went right in the boat along with the engine install.

    Worked out really well for me.

    Thank you for that and your helpful reply.
    Registration @ Boliven is free , check it ou! Your welcome BTW Thank you! been curious how you adapted that Place Hydraulic set up to the Panther-Vator

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    Senior Member Double A's Avatar
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    I will send you a picture of how I did that Hydraulic Assembly. Initially, in my mind it started out a little complicated...then the more I looked...it actually turned out Really Really simple. Funny how that works.

    I'm going to take a stab at this intake thing this week. Right or wrong. Got to try something. I was thinking of a berk style rock grate incorporated. Something like that. What are your thoughts on the standard intake grate it has now? Ditch it or keep it?
    Soon as I get the bottom work finished on the boat I can clear my mind and give this intake a more serious thought.

    Thanks.

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    Cas
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    Double A,
    You might want to check out what 78_Tahiti has been doing with his Panther diverter, it's some pretty cool stuff!
    http://www.laidbackboatersboard.com/...ults-t494.html

    Tom,
    Not sure if you remember but I posted a bunch of info on that adjustable intake that Panther used to do back on my original Panther Pump board. Panther quit selling it do to a couple of high speed accidents where someone in the boat closed off the intake too much at speed and caused the boat to flip. As of 3 years ago, Panther still had the plans for it for sale but since Steve has retired, I don't know if it's still available.
    I would have just posted it all again but since I'm older now, I don't remember all the particulars. I also lost the hard drive that had all my Panther tech/spec sheets and all the different upgrades.
    The only things I can remember are the Power Shift, the Speed Trim and what they called the "Hot Lick" which was an insert to reduce the nozzle size. It was also used in conjunction with the Speed Trim and was installed similar to their current diverter deal.

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    Senior Member Double A's Avatar
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    Thank you Cas. You know the initial intake area on my pump is actually a part of
    the boat mold. It is not Rectangular like a berk type. It is more like a tear drop shape. Real skinny at the leading edge of the intake slope. The leading edge of the tear drop it is really contoured with a Bump so to speak. So its kind of convex so to speak. I wonder if the water is losing contact with the boat here (poor load effect) causing an over rev at higher speed.

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    Cas
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    Quote Originally Posted by Double A View Post
    Thank you Cas. You know the initial intake area on my pump is actually a part of
    the boat mold. It is not Rectangular like a berk type. It is more like a tear drop shape. Real skinny at the leading edge of the intake slope. The leading edge of the tear drop it is really contoured with a Bump so to speak. So its kind of convex so to speak. I wonder if the water is losing contact with the boat here (poor load effect) causing an over rev at higher speed.
    Yep, I'm very familiar with the Panthers as I used to rebuild them and work on Panther powered boats as a sideline for a few years. The cavitation at higher rpms is usually because the impeller can't move the amount of water that's coming into the pump which in essence, causes the water to back up. I've seen quite a few boats where the owner added a big engine to go faster and actually lost mph. The engine would just over power the pump and make it slip like crazy.....500 hp max on a fresh pump is really about it.
    A simple example is to move a can with one open end through water to see what happens.
    What's been done in the past is to down size the molded intake by adding about 3/4" of glass to each side. A lot of times that will allow less water into the pump at higher speeds which cuts down on the high revving. The problem that could arise is the loss of hole shot.
    The other thing I've done is to rework the impeller blades to give them a different angle. It's difficult to do with stainless steel and the return for what I did wasn't really worth the effort although it did lower the rpms a bit.

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    Cas
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    DOn't know if you've taken the Stator Housing off for inspection yet.
    Here's a picture of one where you can see the Stator Rings that a lot of times get worn off. Make sure yours has them as it's an area where loss of performance will occur.


    here is what I mentioned above about downsizing the intake. The blackened area is what is filled in. It basically closes the intake down to match the outer chines of the rock grate.

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    Senior Member Double A's Avatar
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    Well I think we are at a max of 450 hp engine probably less... on a fresh pump. So if we were to make a shoe or loader for this you think that would make it worse?
    Maybe I could send the impeller to someone to have it re-pitched a couple degrees.
    I asked Panther about their impeller options. They would not give me any answer on this. No answer at all. The only thing they told me was that they tested their pumps to 1200hp and they worked well with that hp, yet they were worried about my engines cam matching the power curve of their pump..?

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    Senior Member Double A's Avatar
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    Does that have a big convex bubble bump there? I cant tell.

    I will check the stator today and see. Thanks Cas.
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    Cas
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    Quote Originally Posted by Double A View Post
    Well I think we are at a max of 450 hp engine probably less... on a fresh pump. So if we were to make a shoe or loader for this you think that would make it worse?
    Maybe I could send the impeller to someone to have it re-pitched a couple degrees.
    I asked Panther about their impeller options. They would not give me any answer on this. No answer at all. The only thing they told me was that they tested their pumps to 1200hp and they worked well with that hp, yet they were worried about my engines cam matching the power curve of their pump..?
    I'd start with the basics before going out and spending a bunch of money or making major changes.
    Who did the pump rebuild and who did the install? Do you know what any of the clearances are?
    Since the engine is revving up to 5500 - 6000, I really doubt there's an issue with the engine not being matched to the pump. Usually, if the engine isn't matched, the rpms will be way down as will the speed. That pretty much holds true with any of the pumps.

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    Cas
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    Quote Originally Posted by Double A View Post
    Does that have a big convex bubble bump there? I cant tell.

    I will check the stator today and see. Thanks Cas.
    yes, the bump helps load the pump

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    Cas
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    the other thing I thought of doing but never got around to it was to make a rock grate where the outer chines were longer and filled in the intake instead of glassing the bottom. Does that make sense? It would be easier to do and could be tunable to a certain extent. The thing is, it would need to fit pretty tight so as not to add another area where cavitation could occur.

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