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Old 04-10-2022, 03:33 PM   #1
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Default Water in oil, 4.3 litre Mercruiser

I have a 2006 Maxum 1800 SR3 that I have owned since it was new. Every winter, I run the engine up to operating temperature and then fog the engine through the carb. After that is done, I pull the 5 plugs from the engine and drain the water out. I then reinstall the plugs, disconnect the four hoses at the top of the engine and fill them with anti-freeze. After a short while, I then pull the plugs again and drain the engine. This spring, I took the boat in to a local shop to have the fluids changed and they said that there is water in the oil and that they suspect the block is cracked.

While I understand that this is one explanation for water getting into the oil, it seems to me that there must be other possibilities. What is the best way to go about diagnosing the source of the water? I wondered about going ahead with the oil change and then running the boat up to operating temperature for 10 or 15 minutes and then draining the oil again to see if there is water in it again. Is there any way to pressure test the oil system to check for leaks into the cooling system?

Thanks for any suggestions.
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Old 04-10-2022, 05:37 PM   #2
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Compression check each cylinder, then I would probably do like you said and change the oil, run it then see what the oil looks like.

What about manifolds and risers, have you ever inspected or replaced them? I might actually look at those first before running it as they could be leaking water into the cylinder which can cause catastrophic engine failure.
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Old 04-10-2022, 06:45 PM   #3
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Is this a fresh or salt water boat? Raw water or closed cooling? Is this milkshake looking oil/water mix or light sign of water. Has the exhaust manifolds and risers ever been replaced? If the exhaust failed removing the spark plugs will most likely have water run out the holes. Most block crack from freezing occur on the outside of the block and doesnít result with water in the oil. If raw water you can block off all hoses on the t-stat housing and on the inlet one add a shrader valve to the plug which will allow you to pressurize the cooling side with air but donít use more than 15 psi. So will add a pressure gauge to verify and let it sit for a day to see if it looses pressure.
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Old 04-11-2022, 04:04 AM   #4
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Wiigelec. all of the parts on the motor have been there since day 1. The engine only has about 500 hours on it. The exhaust manifolds and risers have never been replaced.
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Old 04-11-2022, 04:07 AM   #5
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Mmwjr,

The engine has raw water cooling. Approximately 90 percent of its tie has been in fresh water, 10 percent in salt. I flush the motor every time I pull it out of the salt water. I didn't see the oil, but from the mechanics comment it sounds like there was quite a bit of water in the oil. Are you saying to pressure test the cooling side rather than the oil side?
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Old 04-11-2022, 11:29 AM   #6
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Yes pressure test the cooling side. The oil is already at pressure when the engine is running plus it would be very difficult to pressurize the oil side to detect leaks as the return passages from the heads vent out the breather caps.
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Old 04-11-2022, 06:34 PM   #7
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So, in terms of the sequence of testing, does it make sense to:

1. remove and inspect the exhaust manifolds and risers
2. check the compression
3. pull the plugs and check for water in the cylinders
4. complete the oil change and run it up to temperature
5. pressure test the cooling side

or would you suggest a different order?
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Old 04-11-2022, 07:51 PM   #8
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I would probably start with the easiest first which would be #3 and do the hardest last which would be #1 and not do #4 until I was fairly sure there was little risk of damaging the engine.
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Old 04-11-2022, 09:51 PM   #9
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3, 2, depending on the results 1 or 5.
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Old 04-11-2022, 09:59 PM   #10
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Thanks.

I just got off the phone with the shop and their opinion is that there is no point in doing any further testing. Based on the amount of water in the oil, they are 100% sure that the block is cracked. I'm just wondering if this is the point to suck it up and go ahead with dropping in a re-manufactured engine or whether it is worth going to another shop for a second opinion.
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Old 04-12-2022, 01:22 AM   #11
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Just how much water did they say? A dribble, a cup?
2 nd opinion is always the way to go.
I would go with changing oil and filter and run engine on muffs to see if you get water in oil. (Note there will be water in oil after you run engine up to temp, then drain oil to see how much water there is.)
Go from there.
Just my 2c.
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Old 04-12-2022, 01:26 AM   #12
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IMO shops take the easiest path since they have to guaranty their work. If you donít know how to perform further investigation yourself and are willing to spend the money to replace the engine go ahead. Did they give you a quote yet? Expect around $6K.
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Old 04-12-2022, 04:01 PM   #13
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So you do your own winterization but not your own oil changes?
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