I had an A4 in my previous boat. The exhaust manifold was connected to a high loop and the water from the HX was injected well below the top of that loop. I never had a siphon break and never had any flooding issues. But the water flow issues are dependent upon the level of the engine relative to the waterline. But a high exhaust loop (mine was insulated) should stop any water from entering the engine EXCEPT if you are cranking and it doesn't start.