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Hydrolock

Discussion in 'Technical Discussion' started by 1000 islands, Aug 27, 2015.

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  1. 1000 islands, Aug 27, 2015
    #1
    1000 islands

    1000 islands Member

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    Apr 20, 2013
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    Location:
    Ivy Lea
    I am currently in a dispute with a marina about some repairs they made to my boat.

    During a discussion about one engine (7.4L Merc) having difficulty turning over, the mechanic said that was because of a leak in the manifold which was causing, what he called, hydraulic meaning hydrolock. Therefore that was why the engine was difficult to turn over, not because of the batteries.

    I said I believed that if hydrolock was the case, then the engine would stop turning completely and lock-up.

    He then said that not always, sometimes the water will seep down through the piston past the oil rings and relieve some of the pressure.

    Am I nuts or is this truly the case and the engine can turn over buy slowly.

    I am not a mechanic by any means, I was always under the impression that Hydrolock is just that water in the cylinder will not compress and locks the engine up.

    I have not had the opportunity to ask another mechanic I know and I reakky don't care to if I'm wrong.
  2. K1W1, Aug 28, 2015
    #2
    K1W1

    K1W1 Senior Member

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    If your cylinder is full of water it would turn so slowly that the starter would be smoking before it got through one revolution if it even got that far. The easy way to verify if there is water in it is to remove the spark plugs and wind her over, if there is water in one you will see it
  3. Capt J, Aug 28, 2015
    #3
    Capt J

    Capt J Senior Member

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    I have seen an engine or two that was very difficult to turn over because of spun main bearing(s) also. Take all of the plugs out and turn it over, see if any water comes out, how fast it spins without any compression, then go from there, too much ignition timing can make it hard to turn over as well.
  4. Capt Ralph, Aug 28, 2015
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    Don't get to carried aweigh turning a motor over with water in a lung.
    I have witness a bent rod from it.

    Pull the spark plugs, disable the coil(s) and try again.