Water in Oil

[bullhead93]

Mercruiser Model MCM 4.3 EFI ENGINE 0M090084
Water in crankcase remove spark plugs water came out of cylinders 6,4,3, removed oil add new.Did a compression test on cylinders 6,4,2 i have 240 psi on cylinders 5,3,1 i have 190
I've rebuilt a few engines work on many cars but not to good on trouble shooting im thinking hopefully blown head gasket would like to understand what happen my first boat

 

[ESGWheel]

Can you provide the history of this motor and what was going one prior to this discovery of water in the oil. Example it overheated and had to be towed home, etc.

 

[Bt Doctur]

all on the stbd side can indicate a cracked manifold and/or riser

 

[bullhead93]

Can you provide the history of this motor and what was going one prior to this discovery of water in the oil. Example it overheated and had to be towed home, etc.

me and wife retired sold house moved to bullhead city bought it off a older gentleman said he was the second owner and and its alsways been in his garage said he he he did all the maintenance himself change fuilds etc. said he was a mechanic in the air force said it been sitting in his garage 1 1/2 years he does get around every good he took real good care of it told me he would take us out to the lake i look at the motor check oil and fuilds eveything look good we went out next morning couple hours on lake look over at one time he look tired we bought he took it to our house i drove him home and the wife fellow he didnt look so good the next day i put a removable tongue on trailer thought i would change oil and here we are.I did call him and he felt felt bad wanted to give money back i told him maybe it was just a blown head gasket said keep receipts

 

[ESGWheel]

Thanks for the background. Frankly I am having trouble connecting the dots.

• Dot 1 > oil looks good and took it for a test drive, all is fine
• Dot 2 > Put it on the trailer and took it home
• Dot 3 > Decided to change oil and found water in the oil and stbd side cylinders.

What I am struggling with is between Dots 2 and 3 > it seems improbable that at the last minute of the test drive - when putting it on the trailer - there was a failure that went unnoticed that introduced water into these areas. While possible, it just seems unlikely.

Was the oil when you checked it and discovered water all milky? This would be an indication there has been water in the oil when the motor has been run.

In terms of troubleshooting (T/S) and getting to root cause, it could be as bad as a cracked head or block, a cracked riser or manifold or a blown head gasket. While one T/S technique is to pressure test the water jacket its not so simple. Easier to pull off first the riser and then the manifold and inspect these for cracks or internal rust ‘holes’. Thus, suggest start there. If all looks good, then you are into pulling the head.

Also, the compression test numbers are way too high so there is probably something wrong with the gauge.

 

[Scott Danforth]

any cranking compression way above 150 is either water or oil in the cylinders, or a bad gauge.

verify your gauge, however I bet if you pulled all the plugs and turned over, you will find that water comes out cylinders, 2, 4, and 6

all bad on one side would indicated cracked manifold or failed riser

was this a slip-kept boat, or was the boat just not winterized properly

nearly never a blown head gasket.

 

[Lou C]

Is this one of the Merc 4.3s with the one piece exhaust manifolds (‘96-‘99), if so these are known for failure & leaking water back into the cyls. There are conversion kits to convert those to the conventional 2 piece style….

 

[bullhead93]

First and foremost, I want to thank you all i've read all your post .I took of exhaust manifolds did'nt see anything so off came intake manifold. I could see on number 6 cylinder water was getting in to intake went back to exhaust look at it carefully and found a hole the size of a pencil eraser in number six cylinder.
Everyone who reply to my post said exhaust or intake if i had'nt come across this forum and you all i would've went to the heads .once again THANK YOU.
L

 

[bullhead93]

Lou C yes it is a one piece manifold and There is conversion kit can any of you tell me of a place i might find the pair from what i'm seeing it not going cheap.Welcome to the world of boating.

 

[Lou C]

Merc makes an OEM kit, and Barr Marine makes an aftermarket kit, I have used Barr with good results on my OMC, which also had the one piece V6 exhaust although I never had water leaks from those, but they were NLA when it was time to replace them....
Here's a link to a place selling the Barr version....

Barr Conversion Kit for Mercruiser V-6 GM 4.3-Liter from One Piece to Two Piece

Barr Conversion Kit for Mercruiser V-6 GM 4.3-Liter from One Piece to Two Piece

marineengineparts.com

Not cheap but it has everything you need to convert. No one except GLM made a kit for my engine (OMC) but due to GLMs lousy rep at that time (don't know if it's better now) I elected to put my own together from Barr Marine's OMC/Volvo manifold & elbow kit with additional OMC/Volvo parts needed to convert to the later style. And at the time I think the total cost was about $1200, but that was like 8 years ago. It all fit like factory with no leaks. The cost, well it is what it is. Bad marine exhaust has killed many inboard engines!

 

[ESGWheel]

Well, this is good news that you found the issue. While I like to try to help, I am also trying to learn. I am a ‘lifelong learner’ as they say. As such I am not familiar with the one-piece manifold and riser so could you please post a picture of it? Also, I would be interested in the cylinder 6 hole > can u post a picture of that as well?

Also agree with using Barr, I did, and am happy with them. Also see this post on replacing manifold and risers for some tips and ticks link.

 

[Scott Danforth]

Barr is one of the casting houses for Volvo Penta, Mercruiser, PCM and others aw well as Edelbrock. So they have pretty good stuff.

The batwings were a bad idea dreamed up by accounting. Core shift meant the walls were either paper thin or really thick they only lasted a few years in production

 

[bullhead93]

 

[bullhead93]

one more question are there certain things i need to do with motor after a day at the lake and is the propeller suppose to have 1/4 in free play

 

[Lou C]

I recall reading somewhere that when GM bought out the Vortec V6s the engines cost l more they came up with this idea to save money. OMC also had their own version of the one piece batwing from 1985-1990 on the V6, I had 3 sets of those on mine (salt water use, changed every 5/7 seasons) and never had a leak on any of them.