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  1. #1
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    Ultra 150 - oil hydrolocked crankcase - questions

    I resurrected an empty hull of a 150 that I bought from a salvage yard. Into this hull I put a used engine with good compression removed from a ski that sat for about 3 years since the last time it ran. I rebuilt carbs, ran new oil lines, and got everything all back together. Other than checking compression, I did not do any investigation into the engine before installing it. Ran perfectly on the hose. Running 50:1 premix since I replaced oil lines. Yesterday was the maiden voyage.

    Ran great for about 10 minutes - was taking it easy, 5000 rpm or less. Felt great, sounded great, very responsive. Then, thunk - dead stop. Locked up based on the sound of the starter. Had power but starter could not crank the motor over. Towed home for evaluation.

    Removed jet pump, was locked up because the impeller spun off the end of the impeller shaft. I thought that was the cause of the lockup, blamed it on me not fully torquing the impeller on to the shaft correctly (was my first jet pump rebuild).

    With jet pump off, however, the engine did not crank any easier than before -- still sounded locked up.

    Removed the plugs, cranked a little easier but still very labored, not nearly as fast as usual.

    At this point I decided to pull the engine back out for further evaluation. Turned out the crankcase was full of 2-stroke oil, and was basically hydrolocked.

    I have to assume that some of that oil was from when the donor ski sat for 3 years untouched? But clearly at some point in running it yesterday, my oiling system was adding too much oil into the crankcase until it hit the point where the hydrolock occurred? And when the crankshaft suddenly came to a stop the loose impeller spun itself off the threads until it contacted the wear ring?

    So, now my question revolves around the check valves in the oil nipples on the carbs and the engine block. I used my Mikuni pop off tester to see what kind of pressure those valves would need to pop open and allow oil flow. All are very low (2-3 psi) except for the nipple on the rear balancer -- this one can be pumped up to 15-20 psi and very slowly leaks down gradually. I have another spare engine standing by and the rear balancer nipple acts the same way, so perhaps this is the correct behavior in that location?

    I'd appreciate any input about this situation. Thanks!

  2. #2
    steve45's Avatar
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    Well, that's weird!

    Don't try to start it with the pump removed. The driveshaft can move around and wipe out your bearing holder and drive coupling.

    I can't believe that it could run with that much oil in the crankcase. I suspect that perhaps it was towed too fast and water got pumped through the jet pump into the cooling system, where it flooded and backed up into the cylinders. I've never seen this happen from towing, but they say it can happen. Perhaps your case had oil floating on top of the water.

    As far as the oil line pop-off valves, I've never tested the ones for the crankcase, only the carbs. I've found those typically open around 4 PSI, so I think you're good there. I don't know about the others.

  3. #3

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    That does sound strange to be that full of oil after it was already running... Were all three cylinders full of oil, or just one? And, was the crankcase so full, it drained out of the reed openings?
    Once drained, can you turn it over by hand easily?

  4. #4
    SplishSplash's Avatar
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    Even if there is zero resistance, there is no way a running motor can hydrolock on the oil. It would have been smoking like a chimmny before.
    The pump cannot pump that volume of oil to completly fill a running motor to lock it up. There is just no way.

  5. #5
    steve45's Avatar
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    Quote Originally Posted by DosUltras View Post
    Good question - I wish I was paying closer attention when I tore it down. All I know is that after unbolting all 3 jugs the bilge was full of 2-stroke oil. I was pretty pissed off at the time so I was not as observant as I should have been.
    So was the crankcase full of oil, or the bilge?

  6. #6
    steve45's Avatar
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    Sounds to me like the oil supply hose to the pump came off or split, filling the bilge with oil an causing the engine to seize when it ran without oil.

  7. #7
    steve45's Avatar
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    Well?

  8. #8
    SplishSplash's Avatar
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    So it was still cranking (spinning) after it locked up when you were trying to restart it?
    Sounds like either it was starved for oil as ther was oil in the bilge or it lean seized and was too stuck to restart.
    Once they cool, the will rotate again, but damage is done sadly.

    Was there any oil left in the oil tank? Or was it all in the bilge?

    Steve45 knows his Kawi's, I agree.

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