next time,take hoses that head to the exhaust off and let them dump.then check your oil.

Yes,i try it today.
i have now open gaskets between exhaust and risers. There is other choice too, restricted gaskets.
But i dont think that causes problem.
i mean, open gaskets maybe let more water flowing thru exhaust.
I have raw water cooled engine.

look for leaks betw, manifold and risers,,doesn't take much to get water sucked back.

Looks better now.
i run engine wirhout water in exhausts, oil level stays same.
Then i run engine normal with water in exhaust about 20minutes idling, engine is full warm, i used my silent choice y-pipes next to risers.
Now oil is about 5millimeters upper than when i start engine, thats not good but:
When i check oil filter oil looks better, there is still white but it looks more like oil now. Oil filter is only half full.
i think that oil is now so hot that it dripping easy back to oil pan.
I wait 3hours and when engine is almoust cold i crank oil pressures up without starting engine.
wait 15 minutes and check oil level and dipstick is same level than beginning.
My Clymer book says 27-34nm torque specs for riser gaskets. Everywhere else it is 41nm. I think they been loose and water is leaking there alltime. Now they are 41nm some little more. When engine is warm i torque those little more ...

Clymer is a terrible manual and may have errors, but torque is at least close. Merc manual list 34nm for riser to manifold
The exhaust gasket should be
https://www.mercruiserparts.com/863724-gasket

i have now these, do i have to change those?

The style I listed are better if you start having a over heat issue, the gaskets will help keep more water in the block

The issue you have now is not a heat issue, so I wouldn't worry about the difference. I don't see that gasket as being the issue right now

I'd worry that his gaskets are dumping alot of water.marko,do you remember what style exhaust riser gasket that came off?

Did you use thread sealer on the head bolts?

Yes. Yesterday i run engine about 30minutes and oil level stays same. I think my riser gaskets were too loose before.