1997 Mercruiser 3.0 LX - oil water mix pushed up through carb! Very exciting

[CPro]

I fixed the idle issues that I had earlier posted about (new fuel/water separator and new filter before the carb).

The boat was running well in the driveway on muffs, idling perfect, etc.. so I launched it today for a quick run to verify everything was good.

When we were running the boat did stall out a bit, but it started right up and we idled out the head of our creek. Once there I went to open the throttle and it immediately bogged down...white smoke was coming out of the exhaust and the boat continued to bog down and stop dead in the water. I lifted the engine cover and found that a slurry of oil and water had pushed up through the carburetor and flame arrestor and had spread all over the engine. It was a mess. It looked like coffee that went too heavy on the creamer. My 8 year old asked if we were stuck, to which I replied that we were fine and that we would just paddle home. I paddled for about 20 minutes after which I was spotted by a benevolent neighbor who towed us back to our community ramp.

Once home I immediately pumped out the oil (it was completely contaminated with water) and removed the head. 3 of the 4 cylinders had a ton of water in them which I emptied, dried the pistons and cylinders and then coated them liberally with oil.

I also removed the drain plug from the oil pan to completely drain the oil/water mix.

I assume this was a failure of the exhaust manifold and/or the exhaust riser? I'm not sure what else would cause this? These parts were about 4 years old, which I did not think was too old. I inspected them last year and didn't think they were past their lifespan. I had checked my oil right before this happened and it looked 100% clean.

Please let me know if you have any thoughts on other potential causes for this. I'm also curious what if any long term damage was done to the engine. I did verify that the engine would turn over still, which it did just fine once I removed the head. I did not hear any obvious bad noises, etc..

Is the correct next step to just replace the exhaust manifold and riser and just reassemble to see if it runs? Should the engine be broken down further? How do I clean the remaining oil/water slurry out of the engine? Should I just refill and drain and refill until I get clean oil back in the system?

Thanks in advance for any advice you might have...hoping to get on the water soon!

 

[racerone]

Your location ?---Any freezing temperatures there ?

 

[CPro]

I'm in Maryland. It freezes in the winter, but it was about 60 today. I did run the boat for probably 30 minutes before this...no issues..no contaminated oil. It was when I had it in the water and tried to accelerate that things went wrong really quickly.

 

[Bt Doctur]

sounds like a cracked block

 

[CPro]

I can't see any obvious cracks, but will look harder tomorrow now that I've got it broken down. Is it possible that it could be cracked somewhere internally and that I wouldn't see it from the outside of the block?

I would think if it was cracked I would have seen contaminated oil even from running at low speeds in my driveway?

 

[achris]

...I would think if it was cracked I would have seen contaminated oil even from running at low speeds in my driveway?

Often the crack won't open up far enough to allow water to pass when the engine isn't hot from being run under load. Also, the water pump pressure when running at idle on the hose (and you should only ever run at idle on the hose!) sometimes isn't high enough to push though the crack...

Milky oil, immediately after winter... Yeah, that's a busted block/head/manifold (or all 3)...
And you may not be able to see a crack without stripping it down as it'll be internal.

What was your winterizing procedure?

Chris.........

 

[Scott Danforth]

please explain how you winterized in full detail, step by step

one of the places the 3.0 cracks is internal to the motor at the bottom of the water jacket. the other location is external to the motor just below the head.

 

[CPro]

I have done minimal winterizing for 13 years. I tilt the lower unit down and pull the plug in the block to allow water to drain.

If it was just a crack in the lower part of the block, that wouldn't explain the oil/water being shot up through the carb, would it?

I took another look at the block and don't see any cracks around the cylinders. I'm thinking that it got a slug of water in it from a bad riser and when the pistons compressed the water, it forced it's way through the head gasket to contaminate the oil. I don't quite know how to explain the oil/water slurry shooting out of the carburetor though?

 

[Bt Doctur]

did you pull the manifold drains too, did you probe the hoses to insure draining ?

More likely it came out the crankcase vent hose not the carb

 

[achris]

I have done minimal winterizing for 13 years. I tilt the lower unit down and pull the plug in the block to allow water to drain....

That's not even close to enough, even for 'minimal winterizing'.

The manifold and elbow drains also need to be removed, and the holes probed with a small screw driver or length of stiff wire to make sure all the water is out (rust and scale can and does clog the holes). The large water hose into the water pump also needs to be removed, and the water drained from the hose between the drive and the thermostat housing. The drive should be removed so the water can drain from it properly (water gets trapped between the water pump housing and the bell housing and freezes and cracks drives internally).

I very much suspect the engine has an internal crack, and is allowing water into the crankcase. That's been emulsified and has been forced through the crankcase vent hose (from the rocker cover) and into the carburetor throttle barrel. That's what you are seeing 'shooting out' of the carb.

Chris.....

 

[Scott Danforth]

without probing the drains in the block and the manifold, pulling the large hose and ensuring all the water is out, you most likely have a cracked block from a "thermal-declination induced aquatic phase shift and expansion event"

water in the combustion chamber doesnt get forced out. it "hydro-locks" the motor preventing it from turning until the water drains past the rings which takes a minimum of 30 minutes on a sloppy motor...... in many cases it simply sits on the oil ring and doesnt get past it to the crank case. if your starter is powerful enough to crank with a piston full of water, it will either bend your connecting rod or it will blow out the bore.

if it forced its way thru the head gasket, it would have taken out the head gasket and you would not have compression

BTW, it only takes about 2 cups of water to completely fill a block with a frothy milkshake and come out the breather. once in the breather, it is forced into the spark arrestor

pressure test your block
pressure test your manifold

 

[achris]

... a "thermal-declination induced aquatic phase shift and expansion event"...

:lol: :lol: :lol: :lol: It froze and expanded...Thus breaking its cast iron constraints... :lol: :lol:

 

[CPro]

did you pull the manifold drains too, did you probe the hoses to insure draining ?

More likely it came out the crankcase vent hose not the carb

In hindsight, I think you are right. The oil/water mixture came out of the crankcase vent hose.

I'm not going to screw around with the boat. I've decided to just list it for sale as is & will advertise it as having a cracked block. Thank you guys for your thoughts on this.