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Old 25-03-2021, 22:04   #1
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Mercury 6hp water in oil issue help

Disclaimer, I am not a mechanic and watch YouTube videos to try and figure things out.

So I recently received a 2013 Mercury 6hp MFS6CS outboard. It was briefly inspected by a local outboard shop and needed a new lower end. I was able to order a new lower end and I installed it.

Since then, the motor has only been started on a stand with the water flush hose attached. It ran fine without any issues. After several months I again started the motor on the stand. I ran it for several minutes before getting ready to change the oil. The engine stalled out after 2-3 minutes and I checked the oil and discovered it had water inside. I changed the oil and ran it again, for 2-3 minutes and again discovered water inside the oil.

My question is where is the water coming from. My first and only guess was a head gasket issue. After watching a video I removed the head. I did not notice anything that jumped out (see pictures). The gasket appeared in good condition.

So I am confused, and not sure how water is getting into oil. I donít see any cracks and the spark plug was dry. The top of the cylinder was lightly lubricated, without water. The lifters/push rods had the milky water/oil inside.

Any help would be helpful. I have ordered the new gaskets and plan to put back together unless someone knows another possible cause that I can inspect

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Old 26-03-2021, 05:17   #2
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Re: Mercury 6hp water in oil issue help

Hummmm. Two types of possibilities. One is any gasket that lies between the coolant passages and the valves/cylinder/crankcase, not just the head gasket. The other is a crack in a similar location. You are replacing the gaskets. A dye penetrant kit is not cheap, but may be the only way to make sure. Here are some examples:

One area for suspicion is the connection of the new lower foot. That contains both the exhaust and the water, and you recently disturbed it.
Never let anything mechanical know that you are in a hurry.
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mercury, oil, water

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