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Thread: Run'n that jet out of the water

  1. #1
    AntRant
    On those days when you just want to here that big V8 idle and echo through the neighberhood or just to make sure everything is good for that lake run a thought comes to mind... Can a jet run out of the water? If so for how many minutes? I seen in past forums guys say to connect a garden hose to the engine to keep it cool but how about tht jet??? AntRant

  2. #2
    Heatseeker
    I've been told to never run the jet out of water. I've only fired mine out of water for a second or two, just to be sure it'll fire once I get to the water. I've been told that running the pump dry can cause many problems:wear ring damage, burnt bearings and bushings, burnt packing rings and seals. I'm sure some of the other guys can give you more specific details on why not to do it.
    My advice: Don't do it!
    Hope this helps.
    John

  3. #3
    HBjet
    NEVER RUN YOUR JET OUT OF THE WATER if you don't have to. If you need to run it, first thing I would suggest if possible is to remove the u-joint between the jet and the motor. Then you can run your motor, rev it, do whatever and not have to worry about hurting your pump. If you can't do that, and you just want to idle the motor for a minute, then take a garden hose and put it through the nozzle of the jet until it's just inside the bowl veins (about an inch) Turn the water on full and you should see water running out of the intake and out of the nozzle. Go ahead and start the motor, but do not rev it. Again, try to avoid running a pump out of the water even if you do the garden hose route. Best case is to disconnect the pump from the motor. Good Luck, I hope this helps.
    HBjet
    [This message has been edited by HBjet (edited November 22, 2001).]

  4. #4
    DetroitJim
    Excuse me for being a little contrary in my opinion here, but what exactly is going to happen? The front end is lubed by a grease fitting. The wear ring does not contact the spinning impeller. The tail bearing runs in an oil bath. Not knowing any better, I have run both a Berkeley and a Jacuzzi on the trailer for an hour or more, and nothing happened at all. The tail bearing area and the front gland got slightly warm, no different than any other spinning shaft with bearings and seals. The boat works fine, so what's the worry?

  5. #5
    XClutchboy725
    I'm with Jim on this one...................
    I've run my American Turbine at idle for extended periods of time and the Jacuzzi befor that with no problems as well!
    I wouldn'r rev 'er up or hold RPMs for any length of time, but a few BLIPS of the throttle don't seem to matter either.
    http://www.goldenplasma.f2s.com/foru...ifferent05.gif
    Just my experience and opinion......
    [This message has been edited by XClutchboy725 (edited November 22, 2001).]

  6. #6
    1quickjet
    About four months ago, I asked Greg Shoemaker the same question. His reply was never run it out of water for very long, but a minute or two when necessary probably won't do much harm. We didn't get into the specifics, because, as always he was very busy. DJ makes a valid point, but I always play it safe when in doubt. Fortunately for me, I live only twenty minutes from the lake. http://free.***boat.net/ubb/smile.gif

  7. #7
    JetboatJon
    I'm confused.....I just picked up an Apollo with a Berkley A impeller and I was told by the guy it would be ok to run out of water. But not for extended periods of time because the motor doesn't have a radiator like a car if it is out of water. I mean the only thing I would need to do really is just start it up and wake the neighbors up get the oil warmed up a bit then change it. And so far just by going through this particular posting it's 50/50 if ya ask me. I'm not trying to put anyone down but does anyone know the truth?? Tell me, because I can handle the truth!!

  8. #8
    froggystyle
    The pros say don't. After they say don't, they say to plumb a "Y" fitting between the pump's motor outlet (on the inside of the boat unless you have a set back pump) and the motor. On each of these Y's, you should have a valve to control water flow. Hose should be on all the way. A small amount of water should be sent to the rear, going into the pump. More than a trickle, less than a full-on gush. The rest of the water should go to the motor. This is for a variety of reasons.
    A) If you run through the transom headers, you will cook the flappers out of most of them by running them dry for any period. And, if painted or powder coated you will heat them up really fast and trash them. If you have OTT headers, it will not matter unless you get over 2000 rpms anyway, but see "B" why you should do it anyway.
    B) Your engine needs to be cooled. This will cool your engine.
    Two things regarding this.
    1) NEVER turn a cold hose on a hot engine. You could crack the block immediately. Turn the hose on first to gauge flow. It should be coming out of your water outlet and the jet. (probably the grate, and a little out of the nozzle)
    2) ALWAYS shut off the hose before you kill the engine (just before, not way before) This will prevent #1 from happening.
    The pump is water-cooled and lubricated. The rear bearing is lubed, and I know the wear ring should not touch, but somehow it does and gets hot. I think that the water pressure around it keeps it from touching.
    If you have an extraordinarily loose pump, I could see this not being an issue. A full race pump is set up really tight. Even starting it for a second could bring you to zero tolerance just because there is no load on the pump to pull the impeller into position.
    Like HB jet said, the best move is to undo your u-joint. Just make sure you remove anything from your motor that could flop around and do damage.
    Though expensive, and space consuming, this is one thing that a jetaway is really good for. You can release the union and do whatever to your motor, and disengage the jet completely in about two seconds. I will be getting one for the pickelfork for sure.

  9. #9
    flat broke
    Originally posted by DetroitJim:
    Excuse me for being a little contrary in my opinion here, but what exactly is going to happen? The front end is lubed by a grease fitting. The wear ring does not contact the spinning impeller. The tail bearing runs in an oil bath. Not knowing any better, I have run both a Berkeley and a Jacuzzi on the trailer for an hour or more, and nothing happened at all. The tail bearing area and the front gland got slightly warm, no different than any other spinning shaft with bearings and seals. The boat works fine, so what's the worry?
    Well, I'm definitely not the authority on the subject but I'll point out a couple of areas that might be of concern. First is the warmth you feel on the front bearing and gland area. Yes it doesn't seem to get too warm, but remember that the packing material is designed to be cooled by water forced into the packing by the pressure in the intake. Without that water, you could cook the packing and be looking at a leak or worse.
    The second issue has to do with a couple of things but basically it relates to the impeller and wear ring. If you look at your jet, there is quite a bit of un-suspended area on the input shaft. The reason the design doesn't need another bearing in the middle is because when the boat is in the watter the impeller ballances itself with the water that it loads. Without that water you will incur torsional loading on the shaft and depending on your impeller/wear ring clearance, you could end up torqing the impeller into the wear ring on the side of the pump that falls in the direction of the shaft rotation. This would be done by reving the motor out of the water. The last issue is the balancing of the impeller(or lack thereof) and the front and rear bearings. Since the impeller is not ballanced it can setup odd wear patterns for the bearing surfaces on the shaft when run out of the water. Once again, the impeller needs to be under load to balance itself While this probably wouldnt happen after one quick 2 minute out of water situation at idle, it can happen.
    The bottom line is that if you spend time and or money to ensure that your tolerances are tight inside the pump, you're probably not going to risk ruining the work that has been done over running the boat dry. If you do have to run it out of water, make sure you dont do the 0-5000 RPM drill on it as you're sure to cause problems in the long run.
    Just my $.02,
    Chris

  10. #10
    JetboatJon
    Now as for disconnecting it completely from the u-joint going to the impeller I'm guess it's just like removing a driveshaft from a RWD vehicle am I not correct? Do you also have to make marks on the u-join and where it connects so it lines up like it did before you removed it, is there some kind of balance as for weights?

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