Milky oil, 1998 9,9 Mercury 4 stroke

[Gustav1980]

I have problem with milky engine oil. 20 minutes running after oil change it turns milky, if I continue drivning it drops milky oil from the crankcase ventialtion and the oil stick overflows.
I have change the termostat. And the engine works well, start easily and good power.

I have removed the powerhead. What is the next step?

 

[bigjohnson]

Change the crank shaft seals and o rings and head gasket.

 

[Jhanratt]

X2. I would suspect Head Gasket, Powerhead crankcase gasket or maybe the lower crankshaft seal.
I had a similar issue but it was much less acute. My issue was the thermostat stuck wide open. Engine running cold.
I would advise you to solve the issue and do several oil changes to ensure the engine is free of all water.
The sump under the powerhead is deep and the oil is likely a bit "stagnant" at the bottom. I'd clean and dry the sump well while your powerhead is off.
I lost a valve spring due to corrosion caused by water in my oil and my piston collided with my valves. It got expensive FAST.
Search my name for details on that fix.

If its a warped head you can probably sand it smooth. I completed this repair on a 20 hp Johnson 2 stroke on the advice of a forum member. (search my name for details.)

Good Luck!

 

[Gustav1980]

Finaly, I removed the cylinder head. And next to the lowest valve there is rust and a small hole. The hole goes straight into the cooling channel.
I think I need a new head?

 

[Gustav1980]