then the exhuast system floods when the engine is shut off if the intake is
left open.

... if the exhaust
manifold ( at the water injection point) is below water at any angle of
heel,

no ****, Sherlock. **That** is forbidden. And it only took you nine days
to
figger it out.

It IS NOT forbidden. It is very common. The requirement is to have a siphon
break. Wake up jaxie, the majority of sailboats are setup like this,
including
the boat in question. All your huffin' and puffin' doesn't change the fact
that
you made a major blunder and now you're trying to save face.