Mercruiser 3.0 water in oil

Scott06

Admiral
Joined
Apr 20, 2014
Messages
7,123
I would expect you need to change the oil 2-3 times. Keep changing until it’s clear. Use cheap oil only need to put 3 qts in

yes based on what you say moisture likely was in engine and git mixed in oil when you ran it.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
13,349
When I had water in the oil and 2 cyls from a blown head gaskets I changed the oil and filter 4x. Try running it on the water and changing it after it gets nice and warm. On the water hose the oil will just not get that hot. Then see what happens to it. Since I fixed mine I don't see any milkyness either on the stick or on the oil filler cap even after it sits for the winter storage season. But if you run it and it never warms up that can happen. Make sure your thermostat is not sticking open and the engine actually comes up to at least the rated temp of the thermostat. Some are 160 units and some are 140 units.
 

Searay205

Chief Petty Officer
Joined
May 27, 2018
Messages
471
your testing with a gas, so it has a lot of kinetic energy if you saw zero pressure drop with temperature same than it checked good. if you used water (can't on combustion side) the you would see a drop immediately. when mine holed through it put 5 quarts of water in pan in about 5 minutes so it was quick. testing with air is extremely dangerous. you are creating a grenade. do not go above 20 pig!!!!!!
 

osavchuk

Cadet
Joined
Apr 28, 2020
Messages
16
Thank you all.
Changed oil twice, ran on the hose for 20 minutes. So far no water in oil. I will finish putting the thing together and will take it on the lake this week will update you all when done.
Thanks a lot all of you, really helpful.
 

osavchuk

Cadet
Joined
Apr 28, 2020
Messages
16
UPDATE:
I have took the boat on the lake twice. Ran it about 4 hours, so far no water in oil.
Thank you all for your help
Happy Boating.
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
7,123
UPDATE:
I have took the boat on the lake twice. Ran it about 4 hours, so far no water in oil.
Thank you all for your help
Happy Boating.

I would think you are out of the woods then. When my neighbor didn’t winterize his master craft and it pushed a core plug out , he got one or two uses before the crack opened up, so if you got it good and hot you should be ok.
 
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