I have fresh build -1990 Mercruiser 454 mag with Comp roller cam. Xtreme marine 11-445-8.
Today i test run about 30mins, everythin is ok.
When i check oil dipstick it have more oil than before.
I remove oil lines to cooler snd have milkshake...
Pressure tested oil cooler, it is ok. Then pressure tested 1.2bar engine water lines block,head,intake all is fine.
How water mixing oil?
Do i have too short exhaust pipes in my test bench an have reversion? Can water mix with oil in reversion?
There is some video my engine running today:
edit: i cant link my video here, because im new but here it is, put letter "h" before ttps then it work.

ttps://youtu.be/UOshK1t-ZlM?feature=shared

Tell use how are you doing this?

can the water mix,,yes
are there any exhaust leaks in the system?does it miss fire while idling?

Here is a better link to the vid:

Engine and oil not getting up to temp. Condensation forms and you get a milkshake. Fought it on some NA 555s and really had me scratching my head. If it’s running well I’d put it in the boat and run it under load. Bet the problem goes away. Obviously after you change the oil before putting it in the boat. 🤣

after seeing that video,,put more tilt into your engine when its running.the exhaust is way to flat,put more angle.

I agree and idle rpm maybe a tad too low. 800ish should be okay.

I Think it have some miss fire, before it warms. No exhaust leaks. I check spark plugs, number 4,5,6 has water sparkle and exhaust elbow have some little rust on exhaust side.

Blocked water hoses which goes to risers and exhaust manifolds, then i make diy tool with pressure gauge, car tire valve, some hoses and attach that system to oil cooler water hose that goes in the engine. Then put air compressor 1.2bar in the system.

Maybe that is true, but there is somethink else too. Im using now engines 2x20mins. 20mins yesterday and 20mins week ago and oil is like cream. Condensation forms some water to oil, but not that much.