Milky 4 Stroke Oil

[King Canada]

I wonder if anyone has any experience with this. My 1999 4 stroke 70 hp Evenrude had milky looking oil last weekend so I took it in. The mechanic thought it was most likely caused by condensation. Checked it to make sure it was running warm erough and changed the oil. Took it out today and at the end of 5 hours of idling and back trolling it looked milky again. Could it be related to the idling-backtrolling or do I have a seal or gasket going. There was no excess volume to the oil. I plan on running it back to the mechanic on Tuesday. Anybody else experience this?

[ChemMechanicInc]

Well, yes, but the oil level was high, and smelled of gasoline.

I think when you start tilting a 4 stroke engine the way we need to to trailer, etc, a few things start to get goofy.

I guess I compare it to my truck and what may happen if I tipped it almost perfectly vertical and then shook it up like a can of pop (trailering, turns, stopping, etc)

Sorry I can't be of more help.

[iffy]

I've ran into that on a couple early model Yamaha 115 4 strokes. There was a seal that was leaking back into the crankcase, and Yamaha issued a service bulletin on the problem. Not sure whats going on with the OMC, but its probably a seal or gasket. Don't run it like that. The engines internal components require lubrication and water doesnt fit the bill.

[hawghunter001]

yes sir milky oil means water water weans you got to fix it probably a gasket

[CrappiesNeyes]

Not sure if this is your problem but on my Yamaha 115 four stroke I had the same thing happen. It turns out that I had not run the motor "hard" enough yet so the rings had not seated yet. I had been doing alot of back trolling at low rpm and the gas was getting past the rings into the crankcase. This caused the oil level to get high, get somewhat milky, and smelled like gas. As the other poster said, Yamaha had a service bullitin for this that changed the thermostat and some other things to make the engine run a little bit hotter. The mechanic also told me to "go run the motor as hard as I can". I went to Mille Lacs on a calm day and ran her wide open for as much of the time as I could and the problem has since went away. You may possibly have the same problem or you may have a bad seal that is letting either gas or water (hopefully not water) into your crankcase. Good luck.

[theoilman]

Most of the time the oil turning milky means you are getting water in the oil - from several possible ways, but most of the time from the cooling water. Typical problems are head gasket or cracked head. Also, there are a number of other gaskets that can leak causing water to get into the oil. You say you have already drained the oil, put in fresh and run it again and the milky problem came back, it is time to consider digging deeper. To continue to run it will definitely cause more damage.

If you need to find a professional for help, post again with your general location and your engine make, etc. - there are many here who can give you good recomendations.