You will get a little water out, not a lot.
The Jet is the item that you unscrewing with the large nut.
If you look between the nut and Inlet manifold that you are unscrewing
it from, you'll see a Banjo coupling with 2 more pipes coming
up from underneath, like an upside down 'V'.
These are coolant pipes that connect to the Banjo that swivels
around the Jet. The water heats the Jet that passes through the
Banjo joint to prevent it freezing.
Be careful not to lose the 2 metal washers that sit either side of the
Banjo joint, and make sure they are fitted correctly on replacement.
No need to disconnect the water pipes, the banjo joint complete
with pipes will just drop down an inch or two. Easily retrieved and repositioned
when refitting the Jet.
The Jet is alloy, the Carbon build up is very hard, and the Jet is calibrated
to an exact size. So I would not recommend drilling it out. If the drill is too big
or runs off you'll ruin the Jet size and bring un-metered air into the engine,
similar to a split vac pipe.
Instead, stand it on end and soak it in carb cleaner or fuel, and keep giving
it a prod with a darning needle or some other such 'podger', until it's
softened enough to break through.
When you get it out, you'll see that it's shaped like an hourglass egg-timer,
and all will become clear.