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  1. #1
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    Default Water coming out of #4 spark plug hole.

    My 1981 mercruiser 340HP 7.4L engine has water in the oil. I am trying to determine if this is due to a head gasket, a cracked head, or a cracked block. I removed all the spark plugs from and cranked the motor. Water is squirting out of the #4 spark plug hole. I doubt this is normal. Head gasket or cracked block? I sure hope it's the head gasket..

  2. #2
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    Default Re: Water coming out of #4 spark plug hole.

    Could have any of those, or it could be a leaking riser gasket which is feeding water into the cylinder via the exhaust valve and leaking down into the oil. That's a long shot though.
    1976 Mark Twain 200VBR w/Mercruiser 233 (Ford 351w) "Heart & Soul"

  3. #3
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    Default Re: Water coming out of #4 spark plug hole.

    First step is take the head off and have a look.

  4. #4
    Petty Officer 1st Class fishinpa's Avatar
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    Default Re: Water coming out of #4 spark plug hole.

    drain oil ,new oil and filter
    do compression test first off !



    start with basics and go on !


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  5. #5
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    Default Re: Water coming out of #4 spark plug hole.

    I put just the #4 sparkplug back in and it didnt even want to crank. The rest of the plugs are still out.

  6. #6
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    Default Re: Water coming out of #4 spark plug hole.

    what if I disconnected the hose to the risor and removed the #4 plug again and crank it to see if water still comes out? Would that be a valid test to eliminate the risor or risor gasket as a culprit?

  7. #7

    Default Re: Water coming out of #4 spark plug hole.

    Pull the intake off and inspect the head and valley of the block for cracks. My buddy did not winterize his boat and when I pulled the intake I found a gaping crack in the head at a water jacket and a crack in the valley of the block. He was recently laided-off and did not have enough money to fix it right, short block and 1 head, so I found a reman head for $150 and JB welded the crack in block. You would have to drill a small hole at the end of the crack to releave the stress and take a wire wheel to it and clean it very well with denatured alcohol. It took 9 oil changes to get the block cleaned out. He has had the boat out several times this year and is still running strong.
    G'Luck

  8. #8
    Petty Officer 1st Class fishinpa's Avatar
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    Default Re: Water coming out of #4 spark plug hole.

    You need to get that #4 hole lubed up good before everything in that hole is rusted!

    sea foam, straight oil or even some 2 cycle oil will do.

    spin engine a little with plugs out and get some more oil in cyl .

    then back to finding what is causing your problems.

    fish
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    Cant imagine why so many wont or dont add their geographic location to their profiles !

  9. #9
    Chief Petty Officer Rscardina's Avatar
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    Default Re: Water coming out of #4 spark plug hole.

    just basic scienec here fellas.. water is not compressable.. and will take something out with it.. example..push rods, valves etc..

    My old merc exhaust riser collapsed..so i found out the hard way what water does entering the chambers.. its wasnt good.. all rods were bent, rockers etc.. total wash.

    If you know you have water in that cylinder you want to find out where its coming from. I wouldnt suggest putting a spark plug on and cranking..you may cost yourself some additional dollars..

  10. #10
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    Default Re: Water coming out of #4 spark plug hole.

    Quote Originally Posted by cdrive View Post
    what if I disconnected the hose to the risor and removed the #4 plug again and crank it to see if water still comes out? Would that be a valid test to eliminate the risor or risor gasket as a culprit?engine has water in the oil.
    Ayuh,... Not really,.... Take the exhaust manifold/ riser right Off the motor...
    Whether it's the Problem or Not, it's gotta come off anyways...
    If it Is the problem,... You'll see the Rust Tracks inside the exhaust cavity...

    Sounds like you might have Freeze Damage, possibly both the exhaust manifold,+/ or the block....
    Unless the rings in that cylinder are Really Bad, it takes a considerable Time to comtaminate the oil that way...
    Any Grease is Better,..... Than No Grease at All.......

  11. #11
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    Default Re: Water coming out of #4 spark plug hole.

    Quote Originally Posted by 6meter View Post
    First step is take the head off and have a look.
    Negative. On a Marine engine with water filled exhaust manifolds, the FIRST thing to check is the exhaust manifolds and the risers. Removing the head is one of the LAST things you want to do. That's a major difference between marine and auto engines.

    Bond-o is pointing you in the correct direction, follow his post and you'll find your problem.

  12. #12
    Supreme Mariner bruceb58's Avatar
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    Default Re: Water coming out of #4 spark plug hole.

    Before you take the heads off, you need to run a pressure test on the coolant system and a compression test.
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  13. #13
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    Default Re: Water coming out of #4 spark plug hole.

    I pulled of the exhaust manifold and Riser. Exactly what should I be looking for? The passages look clean. The center where the exhaust comes out is a little black with carbon. I could not tell if there was a problem with the risor gasket because it tore apart when I split it from the manifold.

  14. #14
    Fleet Admiral HT32BSX115's Avatar
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    Default Re: Water coming out of #4 spark plug hole.

    Before you take the heads off, you need to run a pressure test on the coolant system and a compression test.

    YES!


    Don't pull heads before you pressure check the system.

    You can remove exhaust manifolds and still easily do a pressure check......because you would want to isolate the hoses to the manifolds anyway......


    Also, you're not going to have a LOT of water in the oil if a riser is leaking. (unless you have a cracked piston, no rings etc.....)

    very little water gets past the rings during starting and while the engine is running little or NO water gets into the engine from a leaking riser. (it just gets "blowed" with the exhaust!!)


    On the other hand, if you have a cracked head, you will get water into the oil and if you have a cracked block A LOT of water will get into the oil.


    Break the manifold//riser connection and carefully inspect the riser gasket (you'll destroy it but you should be able to tell if it was leaking)

    You could also fill the manifold(with riser still on) with water (stand it up...hook a hose to the lower manifold connection ) and see if the water runs out internally. You'll have to wait for the little bit that goes over the top to drain back if you over fill it.

    Do the pressure check first. You need to check for leaks in the block, heads, and intake manifold first.



    Cheers,


    Rick
    73 de Rick
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    I use xxx oil and have never had a problem........
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  15. #15
    Fleet Admiral HT32BSX115's Avatar
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    Default Re: Water coming out of #4 spark plug hole.

    Quote Originally Posted by 6meter View Post
    First step is take the head off and have a look.
    HEY!... do you know that 6m is open?
    73 de Rick
    ----------------------------------------------------------------------------------
    I use xxx oil and have never had a problem........
    1987 FourWinns 211 Liberator, 7.4L- Bravo III installed by ME,
    Formerly OMG 460 King Kobra powered
    1947 Stinson 108-2 Station Wagon
    , Franklin 6A-335B. Hartzell CS 2-blade prop
    -
    All PM's cheerfully answered! Please ask tech questions in the appropriate forum so everyone's included

  16. #16
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    Default Re: Water coming out of #4 spark plug hole.

    I had pretty much the same problem and am about half way through fixing it. A crack in the manifold let water in through the exhaust ports and I had 4 valves rusted in. I'm waiting now for a price on the manifolds and know it won't be pretty. The heads should be back next week and with a little luck I will be back at the marina by the first of the month. Next fall I'll service it myself. Ifyouy want it done right do it yourself

  17. #17
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    Default Re: Water coming out of #4 spark plug hole.

    My 1994 regal 4.3 lx mercruiser has the same identical problem that happened yesterday, it hydro-locked on me, after atempting to start it over and over I took out the starter, it was the rear cylinder on the port side that filled up with water for me, no water is in the oil at all, was told in another thread that engine ''RUN ON '' may cause this as well, which is a problem for me everytime I turn the engine off, haven't tested anything yet as I am waiting for my starter to get rebuilt

  18. #18
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    Default Re: Water coming out of #4 spark plug hole.-Update

    Engine is apart. Found that the port exhause manifold had a hole in it abd was letting water in the engine. Is it possible for water coming in the port manifold to shoot out of a cylindar on the starboard side?

    Replacing the Manifolds, Heads, and all new gaskets on Wednesday. I am praying that this solves the problem.

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