4 stroke oil looks milky

[greenhornet73]

I have a 2021 Mercury 4 stroke 9.9 I use for trolling.  I just checked the oil before going out tomorrow and the oil looked like milk running off the dipstick.  I’ve ran it twice this spring and it has been running fine.   I ran it all year last year and never saw the oil look like this.  What is it?

[greenhornet73]

I’m reading about it and I’m wondering if this is normal from condensation since I have only been trolling with it at low rpm’s since I have been slow trolling in cold weather under 2.5 mph at all times.  Am I going to damage the motor running it like this if that’s the case or will it burn off if I run it faster?

[Traveling Circus]

I've got the same motor, but an older version. 

2 years ago, I noticed the same thing you are seeing, and pulled the thermostat. It was stuck open, never allowing the motor to reach temp. Changed the thermostat, and problem solved. very easy fix in my case. 

[greenhornet73]

Thanks, good to know. I’ll check it tomorrow.

[strik]

I just had the same issues on a 2015

 

Stuck open  Stat was my issues

 

Nice quick easy fix...

 

 

 

[sherman brown]

checking your thermostat would be a great place to start. but any time you run your motor in colder water and colder temps if you don't run it at a higher RPM long enough to dry the condensation it will mix with your oil. the more times you run in colder conditions at idle will make things worse each time it's used.

[13owhunter]

Some good advice above.  Hope it is a simple fix!  I dont think it was mentioned already but dont run it with milky oil.  That could cause significant damage.  If you change it and it is milky after one or two trips, I would think there is something else wrong.  Doubt a couple of trips would add enough water via condensation to turn the oil milky.  The oil in my old 4 stroke kicker looks perfectly normal after running in cold water barely above idle.  This is a good reminder to everyone to check their oil before every trip!

[stinger]

Another thing to consider is run trolling bags so you will have to run at higher RPMs. The higher RPMs will also generate more amps to charge your batteries if you have that feature.

 

 

 

[chinook35]

8 hours ago, 13owhunter said:

Some good advice above.  Hope it is a simple fix!  I dont think it was mentioned already but dont run it with milky oil.  That could cause significant damage.  If you change it and it is milky after one or two trips, I would think there is something else wrong.  Doubt a couple of trips would add enough water via condensation to turn the oil milky.  The oil in my old 4 stroke kicker looks perfectly normal after running in cold water barely above idle.  This is a good reminder to everyone to check their oil before every trip!

I agree  Change oil and filter before further use. If it happens after another trip or two ( check frequently ) I’d be looking for cracked crankcase or head or blown head gasket 

[greenhornet73]

The thermostat was open when I pulled it out this morning before starting so I suspect it is stuck open.  It “made oil” during this mornings trip so I shut it down and ran my main instead.

[chinook35]

33 minutes ago, greenhornet73 said:

The thermostat was open when I pulled it out this morning before starting so I suspect it is stuck open.  It “made oil” during this mornings trip so I shut it down and ran my main instead.

Made oil ??! 

[greenhornet73]

When I pulled the dipstick the oil started running out meaning it was collecting water so I shut it down.  Looking it up online it appears this is typical for a failed thermostat that is stuck open.

[fish whistle]

9 hours ago, stinger said:

Another thing to consider is run trolling bags so you will have to run at higher RPMs. The higher RPMs will also generate more amps to charge your batteries if you have that feature.

 

 

 

Yup, better oil pressure as well.  

[13owhunter]

If you got a bunch of water in there and think the thermostat will take care of the problem, it would be a good idea to do a second oil change after one trip to make sure you get it all out.  Personally, I would do a third after another couple more trips just to check it.    You could also change it, get it up to temp and run for a bit on muffs or barrel and then change again right after.  No reason not to run cheap dino oil for this purpose.

[greenhornet73]

21 minutes ago, 13owhunter said:

If you got a bunch of water in there and think the thermostat will take care of the problem, it would be a good idea to do a second oil change after one trip to make sure you get it all out.  Personally, I would do a third after another couple more trips just to check it.    You could also change it, get it up to temp and run for a bit on muffs or barrel and then change again right after.  No reason not to run cheap dino oil for this purpose.

Yep, that’s exactly what I plan on doing. Really hope that’s all it was.

[spoonfed-1]

4 hours ago, chinook35 said:

I agree  Change oil and filter before further use. If it happens after another trip or two ( check frequently ) I’d be looking for cracked crankcase or head or blown head gasket 

X2. It ain't condensation.

[greenhornet73]

Yeah, last night I thought condensation because it was milky but the level wasn’t much higher. Today it poured out when I pulled the dipstick after running it over an hour on the lake. It was running fine but wanted to keep an eye on it.  Definitely smells like gas in there.

[spoonfed-1]

48 minutes ago, greenhornet73 said:

Yeah, last night I thought condensation because it was milky but the level wasn’t much higher. Today it poured out when I pulled the dipstick after running it over an hour on the lake. It was running fine but wanted to keep an eye on it.  Definitely smells like gas in there.

Not sure I would run that motor until you find the problem. Good luck.

[sherman brown]

8 hours ago, greenhornet73 said:

Yeah, last night I thought condensation because it was milky but the level wasn’t much higher. Today it poured out when I pulled the dipstick after running it over an hour on the lake. It was running fine but wanted to keep an eye on it.  Definitely smells like gas in there.

if it has fuel in the oil you have a much larger problem. and there is no way it should have enough fluid in it for it to run out when the dipstick is removed.

 

but before I would do anything with what you say about the oil pouring out when you pull the dipstick and the smell of gas I wouldn't run it again and set up a time to take the motor in to have it checked and repaired. it is something a lot more serious than condensation in your oil.

 

my guess would be a blown head gasket or a cracked head. but getting it checked by a certified mechanic will give you the answers to the problem. they might know some other way you are getting water or fuel in the oil. but my first guess would be the head gasket or the head. but 1 more option would be a cracked block but I think that is highly unlikely. these are the only ways I know for water or oil to get in your oil.

 

it sounds a lot like you may have a blown head gasket or a cracked heat. with what you say here I would take a small amount of the oil and place it on the ground or other safe place away from everything that might catch fire. then I would get a long stick or other thing then I would tape a piece of paper on the end and light the paper then hold it to the oil and see if it burns. if it's just fuel and water nothing should happen but if fuel is in it, it should catch on fire in short order.

 

 

[Sean Youngblood]

https://www.walleyecentral.com/forums/showthread.php?t=96806#:~:text=The valves on the motor have'nt seated themselves,it at speed and they should seat themselves.

[greenhornet73]

2 hours ago, Sean Youngblood said:

https://www.walleyecentral.com/forums/showthread.php?t=96806#:~:text=The valves on the motor have'nt seated themselves,it at speed and they should seat themselves.

Interesting conversation in there that is very pertinent to my situation. I trailer long distances with the motor down and also only troll with it at fairly low speeds.  It doesn’t have a lot of hours on it and I can’t imagine it could have a cracked head gasket or anything serious like that so soon.  I’m going to change the oil and thermostat this week and disconnect the fuel line when I trailer it on my next trip out and keep an eye on the oil while I’m out there.  Thanks guys for all the possible factors that might be causing this.

[Sean Youngblood]

  I saw it was mentioned to pull trolling bags which I see is a popular on this site. I don't think I would like putting more drag on my boat or having something else to snag my line on or forget to take out before heading in at high speed. Couldn't you just swap out the high trust prop for a 3 blade prop or a prop with less pitch to get the rpms up and speed down ?

[tyler.woodard04]

Is this a EFI model?

[greenhornet73]

I’m going to talk to the marina where I bought it used last spring and see what they say.  I trailered it all last season and didn’t have a problem so something has happened this spring.  If the thermostat doesn’t do it then I’ll bring it in for service.

[greenhornet73]

It is not an EFI model