The output of the water (in a
wet exhaust system) is the exhaust pipe just after the exhaust manifold

no, it is not. the water injection point is quite a bit after the enhaust
manifold in all low mounted engines. This is done to get the water injection
point well above the water line to avoid eventual troubles.

jeffies, don't confused the water injection systems you see on rod hot boats
(when you admire their dual or triple V-8 engines and silicone babes) with
their engines exposed in gas docks. Those engines are mounted well above the
waterline, so have not need to move the water injection point upward. It is
already more than high enough.