# 8hp Yamaha milky oil



## whiteyes (Jan 26, 2015)

I've got a 8hp Yamaha. When I changed oil a few weeks ago I noticed the oil was very milky. Put in new oil n ran it in driveway and look at oil n it was again a milky color. Been told maybe thermostat or a head gasket. Anyone else ever have issue?


----------



## SemperFi (Mar 10, 2014)

There was a issue last year around this time that was posted. They said was cause by the thermostat wrong temp. They were getting it lake erie water temp cold. It depends on how long you ran the motor in your driveway.


----------



## PromiseKeeper (Apr 14, 2004)

milky looking oil usually has water in it. I don't see where the wrong temp thermostat would cause that. There has to be a crack somewhere in either a gasket or water jacket that would allow oil and water to mix. Did you look at the oil level? Was it over the full mark?


----------



## whiteyes (Jan 26, 2015)

I ran it in driveway for 15mins. I measured the oil when I took it out. Didnt seem to add any to level.


----------



## John Garwood (Jul 5, 2016)

gasket is leaking


----------



## hatteras1 (Jan 18, 2011)

Your definitely getting water in the engine, could be a gasket. Dealer will probably not give you an answer without looking at it.


----------



## nikmark (May 26, 2009)

There was a similar thread a while back on this topic with a small outboard.
https://www.ohiogamefishing.com/posts/2563403

If the thermostat stays open, the engine runs cold/rich and the unburned fuel containing ethanol draws condensation from the air. Does the oil also smell like gas?


----------



## sherman51 (Apr 12, 2011)

a stuck thermostat can cause condensation in the motor causing milky oil if run in cold water. but in most cases I know about its a blown head gasket.
sherman


----------



## hatteras1 (Jan 18, 2011)

sherman51 said:


> a stuck thermostat can cause condensation in the motor causing milky oil if run in cold water. but in most cases I know about its a blown head gasket.
> sherman


YES, POSSIBLE.......... but not in that short of time. compression test/ Leak down test will tell you


----------



## whiteyes (Jan 26, 2015)

I ordered a cylinder head leakage test kit today. Hopefully I'll have it figured out this weekend.


----------



## FishIgo (Apr 21, 2011)

I had a 2015 Mercury 40hp with a faulty thermostat ! The faulty thermostat allowed the motor to sweat on the inside while running in close to freezing water ! It was from
Fishing all day not 15 mins


----------



## little d (Dec 10, 2008)

I had the same problem on a 8hp and a 9.9hp both were 2008 both time i chased all kinds of things and both ended up being the fuel pumps. you will get some just trolling in the cold weather and water but mine were both fuel pumps. you can pm me if you would like. dan


----------



## hatteras1 (Jan 18, 2011)

Do the 4 strokes have a pcv system, or vent to atmosphere?..... Just wondering.


----------



## Popspastime (Apr 1, 2014)

I'm thinking the kinippty pin fell out of the thingamabob and caused the whachamacallit to start a leak. Not a clue..


----------



## hatteras1 (Jan 18, 2011)

Popspastime said:


> I'm thinking the kinippty pin fell out of the thingamabob and caused the whachamacallit to start a leak. Not a clue..


You forgot the Doodad


----------



## little d (Dec 10, 2008)

condensation is part of it in the cold weather, but water and oil will seperate after some time. now fuel will stay milky. in our drag race engines we run no water and will pull out a qt of milk after a night of racing (depends on weather though) the fuel pumps are on the back of the head and come off easy. they dump right inside the crank case when leaking.


----------



## whiteyes (Jan 26, 2015)

I pressure tested the motor n no air leaking from gasket or motor. I think I mite just order a new fuel pump n try it out. Glad it wasn't a cracked motor. Hoping to get back out this weekend to try it. Thanks for all the replys. Keep everyone posted.


----------



## sherman51 (Apr 12, 2011)

I would change the thermostat as well. if its stuck open the motor never warms up leaving a lot of condensation going in your oil. just an opinion that might solve your problem.
sherman


----------



## Shad Rap (Nov 10, 2010)

hatteras1 said:


> You forgot the Doodad


And thingamabobs brother, thingamajig.


----------



## Popspastime (Apr 1, 2014)

Shad Rap said:


> And thingamabobs brother, thingamajig.


Not even going to get into the gongajammer..


----------



## mmtchell (Jul 9, 2014)

It's the thermostat, been there done that ,,, fixed


----------



## SemperFi (Mar 10, 2014)

Sounds to me like thermostat


----------



## whiteyes (Jan 26, 2015)

I changed my fuel pump n went out for a day of fishing. Ran kicker for about 7hrs and oil is still milky. There was a couple of extra ounces came out when I changed it. Next try is the thermostat. I've got it bought just have to change it. Anyone change one on a 8hp Yamaha? Wondering how easy it is n were is it at?


----------



## crappiedude (Mar 12, 2006)

I haven't looked at them but YouTube is your friend
https://www.youtube.com/results?search_query=yamaha+8+hp+thermostat+replacement


----------

