2005 Mercruiser V6 4.3L -water leaking into the engine

I tried to start the motor but it would not start and it wouldn't crank.
When I checked, water was mixed in with the engine oil.
I opened the cylinder head and found that only one side had water and the head gasket was intact.
So, I sent both cylinder heads to the machine shop for pressure test.
The result was no crack in both the head. So they resurfaced the cylinder head and
I assembled it back onto the engine.
I went for a test drive and the engine would be fine for about 30 mins on full speed
but after that, the water leaked into the engine again.
I re-opened the cylinder head and rechecked for any cracks by doing another pressure test.
The result came back the same with no cracks.
On a hunch , I changed the intake manifold. Nothing had changed and the same thing happened with
water leaking into the engine.
FYInly the left side of the engine is filling with watter.
Any ideas or suggestion would be greatly appreciated.

cracked heads ,cracked block, improper install of the head and/or torque pattern and Ft/Lbs

cracked exhaust manifold, water is leaking into the exhaust and being sucked into the cylinders. also check to confirm your exhaust shutters are in tact. that is a shame you did this job over 2 times and no-one suggested the manifolds. ugh

Thank you for your input. It was very helpful as I had a slight hunch that it was the exhaust manifold as well.
Do you think there is a way to test for sure if it is in fact the exhaust manifold?

here ya go follow post #2

https://forums.iboats.com/forum/eng...-testing-exhaust-manifolds-for-leaks?t=288629

Thank you for the link!

sure thing, let us know how you make out