wet spark plugs

[dgp]

i have a 5.7l gmc with a omc 800. rebuilt engine installed in june, running good all summer, oil pressure good, temp 160, lots of power. i was out two weeks ago everything was fine, flushed the engine on the muffs parked it. today i tried to start it, would not fire so i pulled the plugs and all 8 are wet. turned it over with plugs out some water blowing out of cyls. were do i start?<br />should i install new plugs and try to start it? <br />could it be the exhaust manifolds or riser, or flappers. oil in crankcase looks good no signs of water.

 

[scamper]

Re: wet spark plugs

Had the same problem with a 7.4L. One side had water in the last two cylinders. Would drain cylinders and engine would fire and run good. When I shut it off and later tried to start found water in the same two cylinders. Lucky I didn’t bend a rod trying to start with water in cylinder. Took exhaust manifold off and found a crack allowing water to inter the exhaust and run into the cylinders when the exhaust valve open when the engine stopped. When engine was running the exhaust gases forced the water out. Cracked riser will do the same thing. Good luck.

 

[dgp]

Re: wet spark plugs

thanks for the help scamper, i changed the plugs today and it started right away and ran well. I will run it a few more times to check if i get the same problem and then winterize.

 

[The Marine Doctor]

Re: wet spark plugs

dgp...you do not just get water mysteriously into the cyl's.<br /><br />To check if its the flappers, run the engine on the muffs. There should be no sign of water.<br /><br />If there is water you will have cracked exhaust manifolds.<br /><br />Water will destroy your engine.<br /><br />TMD

 

[merc 140 pontoon]

Re: wet spark plugs

I've had some overheating problems, which I believe I've fixed, but let's say I want to confirm that I am NOT getting water in the cylinders (even a small amount). I've never seen water in any cylinder, so I don't know what I'm looking for. I've looked at my 4 spark plugs many times--they are clean, but I don't know if I'd call them "steam cleaned". Looking at a spark plug is so subjective. So do I idle the engine on earmuffs for a while, then shut down and pull the plugs? Do I look inside with a flashlight, or do I crank it over with the distributor wire pulled and watch for water flying out? We hear warnings about water in the cylinders all the time, but I've never heard the "correct" way to check for it.<br /><br />By the way, I recently had my manifold and riser off and couldn't see anything wrong with a close visual inspection (didn't have them pressure tested).<br /><br />Thanks.<br /><br />Steve

 

[merc 140 pontoon]

Re: wet spark plugs

Anybody?

 

[Stanp]

Re: wet spark plugs

Here's a thought. back off the bolts to the exhaust manifold about an inch. slide the manifold back so you can see into the exhaust ports of the manifold. Leave the exhaust below atatched. unclamp the hose from the thermostat housing and reclamp to a garden hose(a little rigging required). Run water and see if any leaks are coming out of the exhaust manifold ports. <br /><br />That should be enough pressure to test for leaks. if there is no water, a leaky head gasket or a faulty flapper valve in the exhaust (if equipped) might be the problem. I'm assuming this engine is raw water cooled.

 

[scamper]

Re: wet spark plugs

How old is your manifold and riser?

 

[merc 140 pontoon]

Re: wet spark plugs

Stan - I did flush test the manifold and riser when I had them off, but not under pressure as you describe. I also ran water from the garden hose through them as you describe, but with the manifold still tight to the engine. I will give your idea some consideration, but wouldn't I have to pull the manifold and replace the gasket?<br /><br />Scamper - Not sure. I bought the boat about 5 years ago. Have put probably a grand total of 20 hours running time on it, due to an annoying overheating problem and just being too busy to boat much. When I had the manifold and riser off, they have a rust colored interior, but no scale build-up. All in all, they looked much better than I expected. The manifold ports to the head look very clean.<br /><br />Steve

 

[scamper]

Re: wet spark plugs

Steve, if you even think you are getting water in your cylinders be very careful. If you crank the engine and a cylinder has water in it you will bend a rod as water will not compress like the gasoline. One way to see if you are getting water is pull all of the plugs, put your finger over the spark plug hole and spin the engine. If you have water going through the system it will show on your finger. There will be moisture on your finger but that should only be gasoline.<br />________________________________________<br />There are old sailors and there are bold sailors <br />but there are no old bold sailors.