If the engine is below the waterline, its impossible to have the exhaust
manifold above the waterline.

really? see below

Unless, of course, you have a "magic manifold"
that can be mounted several feet away from the engine.

You can use a special elbow to raise the injection point a few inches

"a few inches"?? at least six inches above the water line. and there is not a
think "special" about it. the pipe is solid bolted to the manifold, an elbow
turns the pipe **UP**, jeffies, until high enough, then the water injection
elbow is mounted, etc.

what word don't you understand?

but that
does not satisfy the requirement that a siphon break is required if the
manifold
is below the waterline.

jeffies, it is NOT the manifold you need to worry about (anymore than you need
to worry about where the oil pump is) BUT where the water (from outside the
hull) empties into the system, THEREFORE if the water injection point is above
the water line **there is no siphon potential**. None.

jeffies, this is easy stuff. as in E Z.