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  1. #1
    RightOnTarget1's Avatar
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    Lost power and making water fast

    I need some help guys. I've done several mods this winter and gotten power up a good bit. I added an external IC and 4" short intake on my 215SCIC 2007 Speedster 150. Two weeks ago, I was hitting on the rev limiter at about 60% throttle. On Jerry's advice, I replaced the stock impeller with a Solas Concord 15/20R. Today I went out to test it. At first, it ran great. However, after 30 min or so, I was doing a ~5000 RPM run, measuring speed and RPM to compare to my old setup. I came to a stop and turned back the way I had come. When I throttled up, I didn't get any thrust. I got RPMs, but no thrust. I thought I had sucked up some debris. I shutdown to see if the debris would drop out. Then the bilge pump came on. I opened the engine compartment and water was several inches deep. Close to my air intake. I figured I had blown a hose. I let the bilge pump catch up and then started idling back toward the dock. I found if I idled, I didn't get water. If I rev'd up, I'd make water and I couldn't get thrust or very high RPMs.

    I couldn't see the source of the water.

    I got back to the dock and pulled out and went home. Now, I've looked at all my water hoses and don't find any leaks.

    I'm wondering if I have a shaft seal problem. Can't that cause cavitation?
    I changed the prop last night. I rested the shaft on a block of wood while I had the pump off. The prop didn't seem to cause unusual vibration.

    The only unusual thing I saw by inspection is that the prop nose cone (the little one on the shaft) isn't tight against the prop. It seems to have backed off a quarter of an inch or so.

    How do you diagnose a shaft seal problem? Any other suggestions?

    Thanks,
    Jim


  2. #2
    Moderator beerdart's Avatar
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    I would continue to look for trash in the pump. It does not take much. Under vacuum the carbon seal bellows will suck off the seat and leak.

  3. #3
    Maybe a leaky carbon ring? Why dont you pull it out and inspect it. See if its cut or grooved around the outer edge.

    No leak at idle but leak under full throttle would suggest that.. and it would also cause cavitation but not necessarily a great loss in power...

  4. #4
    SPEED COMES 1/10 @ A TIME SpeedFreeks Racing's Avatar
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    pump bolts

    to me it sounds like your pump bolts may have gotten lose or maybe you for got to tighten them.... if so you may have stripped the splines in the prop and shaft. i would pull the pump and have a look see.

  5. #5
    Thats reasonable. He just had it off to do the prop.

  6. #6
    speedskixp's Avatar
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    Check your motor mounts.

  7. #7
    RightOnTarget1's Avatar
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    I really can't see any trash in the pump from either direction.

    I carefully torqued the pump to pump shoe bolts and the venturi to pump bolts. Nothing seems loose now.

    I just checked the motor mounts with a flashlight. They look good.

    How do you check the carbon ring? I'm not even sure how to get to it...

    I thought the 15/20R would be too much also. However, I was pulling over 8000 with it today and set a new GPS speed record. I think part of it is that the air and water are really cold right now. I also think having a really efficient intercooler setup helps a lot. I discussed with Jerry and he predicted perfectly where my RPMs would be.

    Thanks,
    Jim

  8. #8
    Moderator beerdart's Avatar
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    It does not take much to cause cavitation.


  9. #9
    speedskixp's Avatar
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    Quote Originally Posted by RightOnTarget1 View Post

    I just checked the motor mounts with a flashlight. They look good.
    You most likely would'nt be able to see if one is broken. The best way to tell is to lift on the engine and see if it moves. Also make sure that there is nothing at all touching the carbon seal or bellow such as cooling line or air intake. Also check the metal hat that the seal rides against and make sure that you cannot move it. If you can move it on the shaft then your c-clip broke or popped out.

  10. #10
    Eric Ocman's Avatar
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    The simplest of things could have happened here. Many people have had the solas nose cone back off the prop, ride up the shaft and interfere with the seal the carbon ring makes.

    Was is completely loose? Pull the prop and pump again if need be and remove it.

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