Water in cylinders.OMC I/O Chevy 350

[JimeeB]

Strange problem I have run in to. The boat I am working on I discovered water in four cylinders (combustion chamber) Normally I would think blown head gasket or possibly cracked head. However the four cylinders that have the water are directly across from each other on opposite sides of the engine. It seemed strange and highly unlikely that both heads would crack or blow both gaskets in the same place at the same time.... Anyways, I started thinking intake gasket so I replaced it and well same thing happened again. On friday I am going to tear it down again and check the heads ,gaskets, etc all that fun stuff. I also see no water on the dipstick. but there appears to be moister inside the valve cover which I will confirm on friday.Anyways.. in the meantime if there is anyone out there who might be able to shed some light on this for me that would be awesome... I mean I myself have not seen heads or gaskets blow at the same time but that doesnt mean it hasent happened.... Oh its a 1988 chevy 350 ci OMC I/O. sorry dont have the S/N on hand but I can get it if needed. Thanks In advance.

 

[Bondo]

Ayuh,..... Which cylinders are Wet,..??

My 1st WAGuess is yer exhaust manifolds are cracked/ broken/ rotten,....

 

[JimeeB]

Ayuh,..... Which cylinders are Wet,..??

My 1st WAGuess is yer exhaust manifolds are cracked/ broken/ rotten,....

# 3 # 5 #4 #6. and to look at the engine it is incredibly clean manifolds riser and all. Nice and black and shiny no rust at all ahem externally.. I mean they look brand new.. But they need to come off anyways to get to a head gasket if that ends up being the problem so I will inspect them. Thanks.

 

[Turbo-Duck]

Wow, that is strange. Has to be head gaskets, or something internally cracked. Heads, or block. Exhaust manifolds leaking wouldn't cause water to get into the combustion chambers... Would have to be something on the intake side.

Have you had the boat long?

-Gary-

 

[JimeeB]

Wow, that is strange. Has to be head gaskets, or something internally cracked. Heads, or block. Exhaust manifolds leaking wouldn't cause water to get into the combustion chambers... Would have to be something on the intake side.

Have you had the boat long?

-Gary-

Well its not my boat, its a friends but he hasent had it long 1- 2 mos. Im not sure of the boat history. However, being that the exhaust manifolds are double wall with with a water jacket surrounding the exhaust gasses to cool them, and from what ive read, it is indeed possible for water to enter the engine if they are cracked. Tomorrow will be an early work day so when i get home im gonna tear into it and see what i can see. ill post what i find.

 

[Turbo-Duck]

Ok, I guess I should clarify, or ask questions before typing... Is it getting water in while running? If so, it would be internal, or on the intake side. If not, it could be the exhaust manifolds.

But, if exhaust manifolds - The only way to get water in those 4 cylinders, would be if it was only leaking in, while the motor was not running, and those 4 exhaust valves were hanging open. That would be a heck of a coincidence.

-Gary

 

[Howard Sterndrive]

I would 1st suspect exhaust manifolds first, then rotten intake manifold 2nd.

You can't go by the outside appearance. The outside is dry and painted- all rotten manifolds look good on the outside. The inside is unpainted cast iron designed to last 10+ years fresh water, 5 salt water. .

Typical with manifold failure for the front 2 cyls to be dry - due to the angle the engine sits at.

 

[Turbo-Duck]

How could water possibly get into the cylinders from the exhaust side? The only way I know, is back through the valves. What are the odds of those 4 exhaust valves being held open while 2 leaky exhaust manifolds have water in the exhaust ports? Pretty high odds in my opinion...

My $$ are on cracked or warped heads - A compression test would be an easy way to determine the condition of the heads. But even then, the odds of both heads having the same problem are pretty high. (Scratching head...)

 

[bruceb58]

My guess is rotten intake manifold like Howard said. Do a pressure test of your cooling system to verify.

 

[HT32BSX115]

How could water possibly get into the cylinders from the exhaust side? The only way I know, is back through the valves. What are the odds of those 4 exhaust valves being held open while 2 leaky exhaust manifolds have water in the exhaust ports? Pretty high odds in my opinion...

Nope. Good "odds"! Have a look at ANY engine upon shutdown. There's ALWAYS a couple of exhaust valves either open, or opening when the engine stops.

The exhaust manifolds are FULL of water all the way up to the risers when running. If there's a riser gasket leak, or crack in the manifold/riser BELOW that water line, water WILL flow through the gasket leak or crack immediately after shutdown and it will run into any open exhaust valve.

 

[Turbo-Duck]

Nope. Good "odds"! Have a look at ANY engine upon shutdown. There's ALWAYS a couple of exhaust valves either open, or opening when the engine stops.

The exhaust manifolds are FULL of water all the way up to the risers when running. If there's a riser gasket leak, or crack in the manifold/riser BELOW that water line, water WILL flow through the gasket leak or crack immediately after shutdown and it will run into any open exhaust valve.

Yep, got that. But the same 4 cylinders???

I'm still betting on the intake, or heads.

-Gary

 

[Howard Sterndrive]

Yep, got that. But the same 4 cylinders???

I'm still betting on the intake, or heads.

-Gary

The water is just barely held out at idle. Then at shut down, as the engine slows from 700 rpm to 0 rpm:
gulp gulp gulp...

 

[JimeeB]

OK.. Got to it earlier than expected.. I have only taken the starboard riser off. I inspected it best I could and it looks solid inside aside from some slight corrosion (this is a fresh water boat BTW) however upon examining further down the exhaust I found that the flapper valve (at least the starboard side) has fallen off of the pin on one side and is pretty much just hanging there. As far as if the water is coming in at rest or while running im not sure. But in another post i read on here this can cause the problem we are having. So. I will get back at it and let y'all know what all I find... fingers crossed that this is the culprit.. LMAO yeah right .. ITS A F!@#ING BOAT. AND.. I have already inspected the intake and reinstalled with new gaskets so im 99% sure this is not where the problem lies.

 

[Bondo]

OK.. Got to it earlier than expected.. I have only taken the starboard riser off. I inspected it best I could and it looks solid inside aside from some slight corrosion (this is a fresh water boat BTW) however upon examining further down the exhaust I found that the flapper valve (at least the starboard side) has fallen off of the pin on one side and is pretty much just hanging there. As far as if the water is coming in at rest or while running im not sure. But in another post i read on here this can cause the problem we are having. So. I will get back at it and let y'all know what all I find... fingers crossed that this is the culprit.. LMAO yeah right .. ITS A F!@#ING BOAT.

Ayuh,... A crucial point of inspection is the gasket surfaces of the riser, 'n manifold, after removin' the remnants of the old gasket,....

A leak There, puts water in the motor,....

 

[JimeeB]

Ayuh,... A crucial point of inspection is the gasket surfaces of the riser, 'n manifold, after removin' the remnants of the old gasket,....

A leak There, puts water in the motor,....

The mating surfaces look good upon initial inspection, but I dont have the old gasket removed yet so who knows... back soon.

 

[Bondo]

The mating surfaces look good upon initial inspection, but I dont have the old gasket removed yet so who knows... back soon.

Ayuh,... The actual flat sealin' surfaces have to be true, level, 'n 'bout 1/4" wide, All 'round,....

As yer peerin' 'round inside the black carboned up exhaust passages,...
Look for Any signs of Rust,.....

 

[JimeeB]

Ayuh,... A crucial point of inspection is the gasket surfaces of the riser, 'n manifold, after removin' the remnants of the old gasket,....

A leak There, puts water in the motor,....

The mating surfaces look good upon initial inspection, but I dont have the old gasket removed yet so who knows... back soon.

 

[bruceb58]

Does the engine ever diesel when you shut it down?

 

[JimeeB]

Ok tried to post some pics but says they are all to big and i dont feel like fussin with resizing them.. Anyhoo.. The mating surface of the manifold is unbelievably pristine. I mean WOW... no signs of any rust in the exhaust cavity of the riser. Riser mating surfaces look fantastic... also no signs of any water leakage on the engine block. Think Im gonna repair the flapper valves, reassemble and giverago tomorrow evening hopefully. saturday at the latest. I mean if this does not fix it it only takes about an hour and a half maybe two to tear it down heads and all, So once again crossing fingers.. will keep everyone posted. And thank you ALL for your input. thats why i love this site..

 

[Turbo-Duck]

Any updates? I'm curious as to what you found?

-Gary