Water in cylinders

spook9702

Cadet
Joined
Aug 7, 2010
Messages
7
I have a 1987 (?) OMC 305. The motor runs and idles fine, no skipping,rough idleling or loss of power. Compression checks out fine. Very small amount of water on dipstick, hopefully condensation. Had water in valve covers dont see it any more, must have burned off. Just changed plugs from Autolite to AC Delco. Before changing them I ran engine for about 10 minutes. Noticed water on the number 3 and 7 sparkplug (poured out of #3 plug). Put in new plugs and engine cranked right up. Could probably pull plugs right now and they would have water on them. I am thinking a cracked manifold. Any suggestions?
 

chaparall villain 2

Petty Officer 2nd Class
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Jul 15, 2010
Messages
129
Re: Water in cylinders

could be blown head gasket , or cracked head hopefully first of the two but if you continue to have water in the cylinders i would pull the head and have it checked for warpage and cracks
 

Borchik

Petty Officer 2nd Class
Joined
Aug 4, 2010
Messages
106
Re: Water in cylinders

could be as simple as a bad riser gasket, there are ways to test the various things before you condemn anything or take it apart.
 

chaparall villain 2

Petty Officer 2nd Class
Joined
Jul 15, 2010
Messages
129
Re: Water in cylinders

good point i would agree , rule other things out before removing head but it does sound like it is located on one side so that should make it a little easier ... check to see if there is a way to bypass the water supply to your riser on that side and run it to see if you still get water in those two cylinders
 

spook9702

Cadet
Joined
Aug 7, 2010
Messages
7
Re: Water in cylinders

Doesnt sound like it is over running. Actuall sounds pretty good for having water in it and possibly cracked block, head or head gasket. Pulled #3 and #7 plugs again and they are dry. Checked riser gasket and it appears to be fine. Some moisture inside riser on the exhaust side where it bolts to manifold. Taking it to marine shop but just trying to rule out what it is or isnt so it wony hurt my wallet to badly. From the cost I see people paying for head gasket replacement on here I might as well drop a new engine in it.
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Water in cylinders

They are actually talking about "Run-On" it's when the engine actually runs after you turn off the key. It's not all that bad if the engine turns the corret way but if it turns backwards (which frequently happens) it will suck water up into the exhaust system.

Your problem sounds a lot like a leaking riser gasket or a crack/leak in the riser or exhaust manifold.


If you took the risers off, I hope you didn't put the old gaskets back on.

You should NEVER re-use old (already crushed) riser gaskets.

You can also get water up into the exhaust riser if your shutters are either stuck or missing, and you shut the engine off while underway. (never shut the engine off while you're still moving above an idle)


Regards,


Rick
 

spook9702

Cadet
Joined
Aug 7, 2010
Messages
7
Re: Water in cylinders

Thanks for the explanation of deiseling (sounds like a timing issue). No, it shuts down fine and starts fine. I will be replacing all the gaskets on that side once I figure out the culprit. Just trying to narrow it down prior to taking to marine shop. Drained the manifolds and alot of rust particles fell out. The guy that sold me the boat said the manifolds where brand new. Yeah, brand new paint. How do you test the manifold itself for leaks into the exhaust channel? The one time I took the boat out after purchase I noticed alot of steam coming out of the exhaust ports.
 

spook9702

Cadet
Joined
Aug 7, 2010
Messages
7
Re: Water in cylinders

Quick Question,
Why is it that we are trying to cool exhaust gases. This causes alot of problems that could be allieviated by custom headers or other means of exhaust system and ventillation. Is it because of heat build up in engine compartment? Im just curious. Im a car guy, dont know much about boats.
 

spook9702

Cadet
Joined
Aug 7, 2010
Messages
7
Re: Water in cylinders

Thanks for the explanation of deiseling (sounds like a timing issue). No, it shuts down fine and starts fine. I will be replacing all the gaskets on that side once I figure out the culprit. Just trying to narrow it down prior to taking to marine shop. Drained the manifolds and alot of rust particles fell out. The guy that sold me the boat said the manifolds where brand new. Yeah, brand new paint. How do you test the manifold itself for leaks into the exhaust channel? The one time I took the boat out after purchase I noticed alot of steam coming out of the exhaust ports.
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Water in cylinders

Quick Question,
Why is it that we are trying to cool exhaust gases. This causes alot of problems that could be allieviated by custom headers or other means of exhaust system and ventillation. Is it because of heat build up in engine compartment? Im just curious. Im a car guy, dont know much about boats.

Well, for one....the exhaust system would overheat quickly and cause a fire in an enclosed engine compartment.

ALL custom headers and other exhaust systems for marine applications in covered engine compartments are (water) jacketed.

The guy that sold me the boat said the manifolds where brand new. Yeah, brand new paint. How do you test the manifold itself for leaks into the exhaust channel?
:rolleyes: Yeah, they always say that don't they?

Have a look at the top of the message list in the forum. There's some info there on how to test manifolds using acetone.

You can sometimes determine how rusty they are by removing the risers from the manifolds and just looking.

Fresh water manifolds last a fair long time. If the boat is operated in salt, they can be junk in 5 years or so..... Some people pull the risers every 2 or 3 years to inspect when they operate in salt water...

You should probably see steam coming from the exhaust. The water is mixed with exhaust at the end of the risers.

You should never have water in the cyls after shut down.

If you do, the risers, manifolds, gaskets etc may be leaking.


Sometimes "dieseling" can happen if you have carbon build-up on the pistons, plugs, valves, or other place in the combustion chamber.

If that carbon "spot" is glowing when you shut down, it can act like a glow-plug and keep the engine turning or cause it to turn the wrong way.

If the engine was running really hot (severely retarded timing etc) it could also "diesel" ......... It doesn't sound like you have that problem.
 
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