2001 ish 15hp 4 stroke bigfoot milky oil.

[Jhanratt]

So I was planning a fishing trip on the West Coast with my family. I did my annual maintenance this morning. Everything else went well except my kicker. The crankcase oil was full and looked new before I started it (8hours since it was overhauled). I warmed it up and dumped the oil. Unfortunately it was full of water (Milky) after warming it up.

What should I do from here?

For background :

2001 ish Mercury 15hp 4stroke bigfoot
this is a high hours (idling trolling kicker)
it is primarily a fresh water motor with 5-10 days salt/year.
it is well maintained and is in very good overall condition.
Last year an intake valve spring broke and a piston hit the valve.
Over the winter I replaced the damaged intake valve, all springs, all guides, all seals, the head gasket, and the powerhead gasket.
I had a reputable shop do the head work for me because It's beyond my capacity.
The re and re I did myself because that's within my skill set.
All surfaces were clean when re-assembled and the torques were exactly to the specs in the shop manual.
I have run it for about 8 hours in freshwater since I completed the work and it ran like a champ.

Where should I go from here?

I'm considering changing the oil and going on vacation but it's an expensive gamble.
I'm considering changing the oil and running it locally to see if it goes milky again?
I'm considering pulling the valve cover and checking head torques.
I'm considering re-torquing the powerhead bolts.
I'm considering cancelling the fishing trip but my family is set on going.
Is there anything simple to check before I start a pull the powerhead and head gaskets?
I doubt it will have any obvious signs of trouble with only 4 hours of run time.

Thanks for your advice

Jeff

 

[Jhanratt]

So I ripped it apart but I checked the torques before and as I did. Everything was tightened to specification or over. My torque wrench clicked on every fastener without moving it. I don't see any issues with the head gasket or power-head / crankcase gasket but I just don't see any issues. here are some photos I took as I cleaned it all up.

 

[Jhanratt]

 

[Jhanratt]

I'm thinking I'll order a new powerhead gasket / crankcase gasket and head gasket and try that.
If that doesn't do it I'm at a loss. I just don't see any reason it should have leaked. The marks around the water jacket and exhaust are more staining than pitting. A strainght edge didn't reveal any concerns with the head or block.
WTF? It shouldn't have leaked in my opinion anyway?

Thanks

 

[galamb]

Here's a piece that was published in another forum in response to the numerous questions about Merc 4 strokes "making oil". I can't attest to any of the information myself as I have never seen the issue and generally don't work on 4 stroke models but this may be of some value to you:

I get a few customers each year with high oil levels in their 4-stroke outboards and it's really tough to explain why sometimes. So I prepared this to present to customers with the problem and I thought it would make a good FAQ.

Q: Why does my 4-stroke outboard oil level keep rising? I never add any. Shouldn't it be going down?
A: This is referred to as "Making oil". Here it is in a nutshell. Water vapor enters the crankcase of all motors from the atmosphere, and as a by-product of combustion. In other motors, the oil gets rather hot and any water vapor that may condense will steam-off and exit the crankcase breather. 4-stroke outboard motor oil doesn't get nearly as hot, so the water just keeps on collecting.

Q: Is it always water?
A: No. Tiny amounts of raw fuel also leak into the crankcase on the compression stroke, potentially diluting the oil and raising the level on a cool-running motor. Or there could be a fuel system leak. Typically the odor of the latter situation is fairly obvious, but not necessarily. Lack of a gassy smell shouldn't preclude checking the possibility of fuel system leaks. Over choking and frequent flooding will also cause fuel to get into the oil.

Q: Where does the water come from?
A: Three sources. Asmosphere, combustion and fuel. There's always moisture in the air, especially near bodies of water. Some condenses out naturally and collects in the crankcase of a sitting motor. Some comes in right along with the air as it runs. The body of water you're operating on produces a lot of atmospheric water vapor, especially a few feet above the water line ... where the powerhead is. H20 is one of the compounds that forms when gasoline is burned, along with CO, CO2, NOX, etc. Some leaks into the crankcase right along with the other contaminants and mixes into the oil. Alcohol combustion makes mostly CO2 and H2O, so alcohol-blended fuels tend to produce more water vapor than straight gasoline.

Q: Wouldn't my oil turn milky if water was in there?
A: Eventually it will. But oil has some capacity to retain water and it eventually reaches a threshold where it starts to cloud.

Q: Why doesn't the oil get hot enough to steam it off?
A: It can. If the motor is running hard enough to plane the boat, water that otherwise cools the oil isn't splashing on the sump that holds the oil. But boats that are run at non-planing speeds may not heat the oil up very much at all. The water the boat is running in cools the oil which is in the sump beneath the powerhead. That water can keep the oil pretty cool just by splashing against the outside of the aluminum sump.Motors that are mostly operated at sub-planing speeds seem to be especially susceptible to making oil. Many times the complaint is that a kicker used for trolling has the problem, but the main motor doesn't. That's because the main motor is used to get to the fishing spot fast to troll slow with the kicker. One is hot, the other is not.

Q: Why is it a problem with my motor and not my neighbor's?
A: Two things really aggrivate the problem. Cool running temperature of the oil, and the abundance of moisture available that inevitably collects. The environment the boat is kept in, water temperature, the fuel you use, and the way you operate the motor have huge effects on whether or not this is going to be a problem.

Q: Wouldn't a hotter thermostat solve the problem?
A: Doesn't help much, but it helps. Problem is that you're regulating coolant temperature and not oil temperature. The oil will get a little warmer as a result, but the powerhead will be running hotter and that's probably not good. Then consider that if the sump is getting splashed by water, that pretty much cancels it out.

Q: How can I be sure of what is making the oil?
A: You can have the oil analyzed. There are many labs that test automotive oil. Outboard readings may not be consistent with what would be expected from an automobile engine, so interpreting the data could be problematic. But it sure will show what is in the oil. A quick search yielded a lot of labs offering this service through the mail for a wide range of prices. Shop around, but it could be money well invested. One site with abundant information is http://www.bobistheoilguy.com/ They also have a Forum if you have any questions.

Q: So what can I do about it?
A: Right now, the approach is to minimize the amount of contamination allowed to enter. That means keeping the motor as unexposed to atmospheric moisture as possible. Practical in some situations, impossible in others. The manufacturers are also stressing proper and agressive break-in procedures to mate surfaces better and keep leakage into the crankcase (blow-by) to a minimum. Avoid alcohol-blended fuels if you can. Finally, allow the motor to get hot enough to steam-off what water will inevitably collect in there. That'll probably mean running it hard for awhile. (If your lake has a speed limit ... Ouch!)If all of that fails, have the motor checked for gasket leakage. It could be coming from the cooling system. More frequent oil & filter changes may be necessary. But try running the motor hard for several minutes every time you go out. That's the easiest, cheapest, and most enjoyable thing to try.

Q: So you mean I HAVE to open it up and go fast once in awhile?
A: Dang shame, ain't it?

 

[Jhanratt]

Thanks for the post. I'm pretty sure I had a more significant issue than described in the above post. I've had boat for about 14 of its 17 year life and it's never made oil this fast before. It did have some milk in it once before when I changed it but never like this. It only had a few hours on a fresh oil change and it ranged from milky tan to milky grey when I changed it. I just finished putting a new head gasket and both powerhead gaskets last night. I hope that fixes it. As luck would have it the water pump failed last night too. I changed it and I'm heading out on the lake for a more thorough test this afternoon.

One thing I'm wondering about is how much water the "mercury" and other marine fours stroke oils can handle? I normally run Mercury or Lucas Marine but I didn't have any around so I was running standard 5w30 in it. Maybe the additive package is not as good? and it couldn't handle the moisture?

It's got a fresh filter and Lucas Marine in it now.

Time will tell.

Thanks

JH

 

[flyingscott]

Check your thermostat.

 

[Jhanratt]

Thank you yes I checked the thermostat when I changed the water pump. It is stuck open and I will replace it as soon as I can get one delivered. I have always carried spare water pumps but I have never carried thermostats until now. I will definitely carry thermostats for both engines from now on.

I didn't really get much of a chance to test the kicker today. Kids wanted to tube non stop so main power got a work out but kicker did nothing but idle for 10 minutes.
oil looks fine and its runs nice and smooth.

I'll report back after I've had a chance to test it further.

JH

 

[Jhanratt]

Update after a LONG delay. This motor has been running like a champ since the head rebuild. I had a great deal of difficulty getting the oil pump and the crankcase gasket to seal but once that was taken care of it has been great ever since. I did replace the thermostat on both of my engines and I now carry not only a spare pump but also a spare thermostat for each engine on board. It is my belief that my milky oil problem was caused by the thermostat which was seized wide open. This caused the engine to run cold all the time, never achieving operating temperature. This cold engine condition allowed cold combustion temperatures and allowed water vapour to accumulate in the engine oil over time. Since the engine never got warm it never had a chance to "boil / steam" the water out.

No issues for me since I changed the thermostat.
I highly recommend frequent oil changes and replacing your thermostat if you suspect it. If you search my posts you will see that I broke a valve spring due to corrosion and that my valve went into my piston. It is my firm belief that this was caused by corrosion (observed at the broken valve spring) caused by "damp" oil.

If all you do is troll with it like I do then make sure the thermostat works properly and change your oil often. Idling all the time is HARD service!