Oil and water mixed

nukuntry

Cadet
Joined
Aug 16, 2013
Messages
14
I know this is not good, but wanted to ask for opinions. I have a 1996 Bayliner with a 5.7 Mercruiser. Oil and water has mixed in the crankcase. What are the possible causes, and what are the best fixes. I have gasoline engine experience, but not marine engines.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Oil and water mixed

Hello and welcome to iBoats.

Oil in the water is never a good thing. Just to set your mind at ease. This 'marine' engine, is just a normal 350 SBC with a few specialized marine bits on it... So all you petrol engine experience will help you...

The special marine bits are:
Starter motor
Alternator
Fuel pump, carb and fuel lines
Most of the ignition system
and the exhaust manifolds.

The electrical stuff is mostly the same, expect it's set up to be explosion proof.

ok.. Water in the oil. 2 main causes. 1, Cracked engine block, usually due to freeze damage, or 2. corroded exhaust manifolds, allowing water in the cylinders, which then leaks down into the crankcase/oil pan....

As you're new here, and to boats by the sound of it. Serial numbers are king with Merc products, so if you want specific help, please post your engine and drive serial numbers. As the boat and engine are made by different companies, the year of the boat has little relevance to the engine... Which is why we like serial numbers :D

Chris......
 

nukuntry

Cadet
Joined
Aug 16, 2013
Messages
14
Re: Oil and water mixed

Here are the serial numbers off my carb cover. Engine # 0F774660 Transom # 0F665915 Drive # 0F665481

I am relatively sure that it is not due to freeze damage, this occurred just recently during warm summer weather while out on the water for a day. This was another persons boat and I am being given the boat at no cost initially. Repairs will be enough cost. He had not had any issues prior to the engine shutting down while under way. Should I dump the oil/water out of the pan and refill with good oil, then turn the engine over some to coat interior surfaces? The engine will turn over and there are no bad noises coming from it. I have not done a compression check. How can I check to see if it is corroded exhaust manifolds? Thanks for your reply and any advice you may be able to give me. A friend of mine is using this site for help in making repairs to his Searay that has major damage to interior due to water exposure and he told me about all the information he was able to get from here. You guys are great!!!
 

bonzoscott

Senior Chief Petty Officer
Joined
Jul 26, 2008
Messages
745
Re: Oil and water mixed

Welcome to iboats! Chris is the expert and will likely respond after you provided S/Ns. But some normal questions for water oil are:
HOW HIGH did this reach on the dip stick? If it were quarts high, probably cracked block (cooling system pressure test in order).
If the oil level is only say a 1/4 quart higher, maybe head gasket (compression test in order).
If it were faulty exhaust allowing water into the cylinders, then draining past the rings into the oil pan, I would think that you would have had other issues like mis-fire or hydro-lock when you were running (check plugs for light color and water, crank motor w/plugs out & see if water droplets come out).

But check that oil level as precise as you can.
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,093
Re: Oil and water mixed

"engine shutting down underway could allow water to go up the Y pipe into the engine. pull the plugs to kmake sure no water is in the cylinders. drain the pan , put fresh oil in and get it running.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Oil and water mixed

Agree with what the 'doc' says. This engine has the new style shutters, so water up the exhaust on a sudden stop is less likely. (not impossible, but less likely)...

Dump the oil and refill, but if you have a bad manifold/elbow then re-starting the engine will just dump more water into the engine. Pull the spark plugs, being careful to keep them in order. If any show signs of water, then pull the elbow and manifold from that side and check it for corrosion. I see your location is NE N.Carolina. I'm guessing that's a salt water area, and the boat's been a saltwater boat since new... (Ossie here, not exact with my US geography... ;)) If that's the case, and the manifolds and elbows are original, then it's very likely they have let go.... (they'd be 17 years old if there are original. I'd say you have your money's worth.... )

Chris.......
 

nukuntry

Cadet
Joined
Aug 16, 2013
Messages
14
Re: Oil and water mixed

Not sure of the complete history on this boat. It has been run in salty/brackish water by previous owner. I will check the oil level today and post back. The boat was given to me due to engine problems and some wood damage from water exposure to interior of boat. I would like to restore and enjoy. I am just starting at the engine to see if I want to dump a bunch of money into this project. One step at a time. I feel like I can turn it into a really nice 40th anniversary Capri. What steps would be best to start with, in order of priority? Thanks.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Oil and water mixed

Get the old oil out.
pull the plugs and check for water in the cylinders and on the plug ends. Spin the engine over and see if there's any water in the cylinders.
If water evident, pull manifolds and elbows.
If no water evident on the plugs, run the engine and monitor the oil level. If it starts to rise again, find the leak. (block off the exiting water hoses and pressure test the block, heads, intakes (just done it on my engine, not too difficult)...

Chris.......
 

nukuntry

Cadet
Joined
Aug 16, 2013
Messages
14
Re: Oil and water mixed

I checked the level on the dipstick with the boat as level as I could get it on the trailer. It was about 2-3 inches above the full mark. Very milky and thick, when I pulled the drain plug I got a slug of water first then came a milkshake of mix. It was so thick it would hardly run out of the bilge drain.
 

jerlap

Cadet
Joined
Jul 21, 2012
Messages
10
Re: Oil and water mixed

I am having the same issue as you. Have changed the head, intake, exhaust and elbow gaskets. My next step is to pull the water pump and check the seals as the impeller is run off the crank. I am running a 1989 merc 3.7l inline 4 cylinder.
 

nukuntry

Cadet
Joined
Aug 16, 2013
Messages
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Re: Oil and water mixed

I pulled all of my plugs today and only one looked abnormal. Will be checking for bad head gasket or cracked cylinder. Did find out that last trip on water previous owner had gotten stuck in mud flat or sandbar and blocked off water to intakes. Overheated motor. most likely the cause of my problems.
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Oil and water mixed

I am having the same issue as you. Have changed the head, intake, exhaust and elbow gaskets. My next step is to pull the water pump and check the seals as the impeller is run off the crank. I am running a 1989 merc 3.7l inline 4 cylinder.

Howdy,

Welcome aboard!

You have a very DIFFERENT engine compared to the original poster.

It will be MUCH better if you start your own thread outlining your problem...........


Regards,


Rick
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Oil and water mixed

I pulled all of my plugs today and only one looked abnormal. Will be checking for bad head gasket or cracked cylinder. Did find out that last trip on water previous owner had gotten stuck in mud flat or sandbar and blocked off water to intakes. Overheated motor. most likely the cause of my problems.

Not sure of the complete history on this boat.

I am not sure how you can categorically say it's NOT due to freeze damage then...... Before you waste time checking head gaskets, you should pressure check the cooling system.

That will tell you once in for all if you have a crack somewhere in the cooling system
 

nukuntry

Cadet
Joined
Aug 16, 2013
Messages
14
Re: Oil and water mixed

Are there any sites that will give me instructions on pressure testing the cooling on this type of system?
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Oil and water mixed

Are there any sites that will give me instructions on pressure testing the cooling on this type of system?

It's fairly simple. Just treat your engine (cooling system) like it's a container with several openings. (remove your exhaust manifolds and risers ....... or at least disconnect them from the cooling system)

Simply close off all the openings except 2 using whatever common plumbing fittings are available......

Connect a 0-30 psi gage to one of them and a valve to the other.

Connect compressed air to the valve and apply pressure to about 15 psi and close the valve.

The block should hold 15 psi indefinitely. If it doesn't you either have a leak in the places you closed off, or the block, head(s), intake manifold, circulating water pump is leaking.

In a fairly quiet setting, you can usually hear where it's leaking. If it's external, you can use soapy water and look for bubbles. If it's internal, you can usually hear it in the oil fill port.

The 5.7L V-8's frequently crack in the "valley" right under the push-rod tubes and on the outside below the head gasket.... near the core plugs.


Regards,


Rick
 
Last edited:

nukuntry

Cadet
Joined
Aug 16, 2013
Messages
14
Re: Oil and water mixed

Found the problem. Cracked block in lifter valley. In search of an engine now. Thanks for all the advice!
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Oil and water mixed

Any junkyard 350 truck engine of the same year will do the job just nicely... ;) Just change the core plugs to brass and then swap everything over from the cracked engine, including the serial number plate...

Don't forget to do the engine alignment when you drop the engine back in... (of course, remove the drive before taking the old engine out)...

Chris...
 
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