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Thread: impeller woes

  1. #1

    impeller woes

    I've been working on the engine of my msx 150 for four or five weeks. I finally got the engine to run perfectly, and I turned my attention to re-assembling the parts of the pump that I took off so I could pull the drive shaft back to get the engine out. When I tried to start the engine, a just got a loud clunk and the engine didn't crank.

    Looking into the back of the pump, I could see two small places where the impeller seems to have bonded to the wall.

    When I first took the engine out, the pump was working perfectly. I don't get how this could happen when the ski hadn't been started even once. Hadn't even touched the water, in fact.

    Is there any way to free up the impeller by breaking the impeller's contact with the wall surrounding it?

    Thanks,
    FLN


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Pull the pump back off, and check the impeller bearings.

    Either the bearings have gone bad, or the pump was not properly assembled into the ski.

    Each pump section must mate properly with the next. There should be no corrosion or rough spots where each section 'fits into' the next.

  3. #3

    Impeller bearing

    K447:

    Are you talking about the bearing you see when you remove the plastic cone at the rear of the pump. If so, how the %[email protected]# do you get that thing out. It seems to be pressed in, but since the impeller won't move, it's hard to tell.

    Any suggesion on how to get the bearing out? Does it require a special tool? I really don't want to break anything, which, in all honesty, I'm prone to do.

    Any tips would be appreciated. I'm a little frustrated. After working on it for days and days, I finally have the motor working perfectly, and you know all the back and forth I've done on greenhulk; I think I got most of my information from you. And now I have to fix something that hadn't been broken in the first place. But, you know, it's gotta get done, so bitching about it won't help.

    It's just that I'm soooooo close to being done--and it's the middle of July, already!

    Anyway, as usual, thanks for your expertise on all things MSX.

    FLN

  4. #4
    Kosh's Avatar
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    Hi FLN,

    Not sure, I might have already mentioned that the impeller wear lining (stainless steel liner inside in the alloy housing) tends to 'grow' into the impeller locking it solid. The alloy grows and pushed the thin stainless liner into the impeller. I have had to replace this pump segment on both my MSX's for this reason. The replacement is all stainless construction so this will not happen again. Of course this may not be your problem but something to be aware of.

    Cheers

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Arrow How to check impeller stub shaft bearings

    Quote Originally Posted by freelancenovelist View Post
    ... Are you talking about the bearing you see when you remove the plastic cone at the rear of the pump. If so, how the %[email protected]# do you get that thing out. It seems to be pressed in, but since the impeller won't move, it's hard to tell.

    Any suggestion on how to get the bearing out? Does it require a special tool? I really don't want to break anything, which, in all honesty, I'm prone to do...
    Have you removed the jet pump from the hull?

    What I meant when I said check the impeller bearings

    Remove the jet pump
    Undo the steering, reverse and trim cable ends (whatever are present) and any small hoses on the right side of the pump nozzle. Undo the four LONG bolts that hold the pup to the hull.
    If the long bolts are too tight, do not over stress the bolts, or you risk breaking them off. Apply some anti-corrosion product to the threads, and let it soak in. With repeated applications and some time to work in, you should be able to work the bolts loose.

    If it really needs it, carefully apply a moderate amount of heat to the bolts and surrounding metal to heat fracture the corrosion around the threads. Don't apply too much heat, and don't burn the hull surfaces.
    Remove the wear ring section that surrounds the impeller. The impeller should now be in free air, but still mounted on the stator section.

    Check the impeller
    The impeller should spin smoothly, with no bearing grinding, noise, or grittiness. And no wobble or play. And only a little friction in rotation.

    If it passes these tests, the impeller stub shaft bearings in the stator are probably OK.

    While you have the impeller out, check the blade outer edges for signs of friction or rubbing. If there is a sharp lip along the edges, the blades may have been rubbing. Examine the wear ring for signs of rubbing and wear.

    If they are excessive, you can smooth the sharp lips on the blade outer edges down with a fine metal file, but do not over do this. You want a fairly square edge on the blades.

    Check the impeller blade clearance
    Now re-position the wear ring section around the impeller. Make sure there is no corrosion, high spots, or binding where the two sections fit together.

    The impeller should be able to spin smoothly inside the wear ring (also know as the extension ring). The impeller blades should not touch the ring surface anywhere when you rotate the impeller, but the blades must have less than 0.020" clearance to the surrounding ring. Optimal is under 0.010" clearance.

    Check the pump sections
    If all this seems good, then check the mating surfaces where the wear ring will fit into the pump base section on the hull. Again, the mating surfaces should be a clean and smooth fit.

    You may want to apply some anti-seize compound where each pump section joins the next, to ease future removal.

    Check the drive shaft
    Now is a good time to check the splines on the drive shaft, and make sure the small rubber button bumper is in place on the end of the drive shaft.

    Also check the splines inside the impeller nose. Splines should not be rounded off or have tapered/angled edges. They should be square.

    Squeeze some good quality waterproof marine bearing grease into the spline cavity in the impeller. Don't fill it, just add enough to nicely lubricate the splines.

    The grease will also reduce the metallic ringing sound when you run the engine with the jet pump out of the water.

    Prepare to re-assemble the jet pump
    I also run a thread tap into the bolt holes in the pump base to clean out any old thread lock compound or corrosion, and also clean the bolt threads with a die.

    Slide the pump back into place, making sure the sections all fit together properly. Put the exit nozzle in place, and insert the four long bolts.

    Reinstall the jet pump
    When the long bolts are just shy of clamping the pump together, again check that all the pump sections are in line, and fully seated into each other.

    Snug the bolts up, and check again. Make sure the long bolts are not spiraled and are aligned straight.

    Check that the exit nozzle is aligned vertically, so the steering nozzle will be pivoting properly left-right.

    Torque in a criss-cross fashion to the recommended torque. First snug all four bolts to 2ft-lbs, then tighten to 14ft-lbs.

    Polaris recommends blue Loctite 242 on the long pump bolt threads. I would leave it off until you are sure you have the jet pump working properly.


    Replacing the impeller bearings
    If you find that the impeller does not spin smoothly on its bearings in free air, then the bearings in the stator must be replaced.
    Jet Pump Maintenance and Service

  6. #6

    Impeller woes

    Okay, K447:

    Let me tell you where I am in your process.

    Everything is off from the wear ring back. I cannot get the wear ring off or move the impeller, because, much like Kosh says in the reply to this post right before yours, the impeller seems to have expanded in the wear ring, and it has bonded to the wear ring in two small places.

    Now I'm looking directly at the end of the stub shaft which is surrounded by a greased bearing.

    Questions:
    1. Is this visible bearing pressed in? If not, does it require a special tool to remove it? I've tried everything I can think of to remove this bearing (short of destroying it and taking it out piece by piece).

    2. Is it possible to break the hold on the impeller's two small bonded places in the wear ring without ruining the impeller or wear ring? I cannot remove the wear ring until these points are freed. Is there perhaps a compound that can work on the fused points?

    I'll take everything else you said and apply it after I answer these two questions.

    Thanks a million, as usual,

    FLN

  7. #7

    Impellar woes.

    By the way, some of you might have noticed that I already posted this question in an earlier thread. Sorry to repost, but the original thread was hijacked, and there wasn't a good way to get it back on track since there were more responses to the hijacked questions every day.

    Hence, the repost.

    FLN

  8. #8
    BBCaprice's Avatar
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    The bearing you see is easily removed with the stub shaft out of the way. However, the only way to do that is to remove the impeller. You are going to have to get the jet pump the rest of the way apart. Pull it back off the boat and either try soaking the impeller/wear ring with some kind of penetrant; or break the impeller free using force. An impeller removal tool would come in handy here. Wear ring is toast anyway....

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by freelancenovelist View Post
    ...Everything is off from the wear ring back.

    I cannot get the wear ring off or move the impeller, because, much like Kosh says in the reply to this post right before yours, the impeller seems to have expanded in the wear ring, and it has bonded to the wear ring in two small places....

    2. Is it possible to break the hold on the impeller's two small bonded places in the wear ring without ruining the impeller or wear ring?

    I cannot remove the wear ring until these points are freed...
    It sounds like you have a lot of corrosion holding the wear ring into the pump base.

    You need to remove the entire lump together, then work the sections apart.

    Get a long 2x4, slide it all the way up in the pump tunnel on one side or the other of the jet pump body, then pry the rear of the pump left and right. You don't need to move it very far, a fraction of an inch each way will work it loose.

    You will probably get the wear ring + impeller + stator to come out as a corrosion fused unit. This is fairly common

  10. #10
    Thanks, all:

    New, let me say that I am a newbie to the pump section. I mean, it's really straightforward, but I have to ask what probably seem like obvious, or maybe even dumb, questions to make certain we're on the same page. Sometimes the same thing is refered to by two or three different names--i.e., pump, drive, webber calls it a propulsion unit, etc.

    With that said:

    Is this correct?

    In order to remove the whole pump, I have to remove the pump coupler on the end of the pump driveshaft inside the hull. Then the whole thing will slide out with the drive shaft and impeller still connected in the pump.

    I haven't been able to separate the stator and the wear ring. I was wondering if I could use short bolts the same size as the very long bolts that hold the pump together and secure the pump to the water side of the pump mounting wall. This way I might at least be able to free the stator and the wear ring. Any thoughts on this?

    In the end, as with most people, it's a matter of tools. I might not have to buy the impeller tool if I can free up the places where the impeller froze to the wall (they are two very small points, each is only about a quarter of an inch long, almost at 180 degrees apart. The rest of the space between the wear ring and the impeller blades is uniform and completely clear all the way around.

    So,

    Yes or no to removing the driveshaft coupler to remove entire pump?

    If I get the pump off, and the clean up the two points where the blades and wear ring meet, and by clean, what I mean is to smooth any corrosion on the walls and tips of the impeller blade, will that work, or am I doomed to rebuilding the entire thing and buying a new impeller, an impeller tool, a strap wrench, a rebuild kit, and possible a new wear ring?

    God, I hope not. As I said, there wasn't a thing wrong with the pump before it sat for the last five weeks. Now, kaboom!

    Makes me want to buy a kayak. (GRIN)

    Thanks for all your efforts, everyone,

    FLN

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