Does anyone have a good idea of where to attach the pressure hose for the water pressure gauge?

Engines: Mercury 496 Magnum HO (close cooled systems)
I guess it makes most sense to attach it somewhere after the sea water pump (impeller) to view the pressure in the incoming cooling...? (But where do I attach it? Are there any pre-drilled holes that I can use?

My engines are MK4 502's. The water pressure gauges are T'd into the front drain hole on the block. On the #1 cylinder side. Not sure on a 496 if you have that type of a drain plug on yours.

I think I do, but I wonder if water pressure isn't more interesting on the incoming water, since the engines have closed cooling systems. Do your engines have closed cooling?

With your closed cooling Gen 7 496 you will want to put it after the seawater pump somewhere, not in the block. Some of the power steering coolers on the rear of the engine above the bellhousing had a 1/8" pipe thread drain plug on them. That is where I put mine.

Otherwise you might have to T off where the factory water pressure sending unit is, which is on the seawater pump itself.

Wonderful! Thanks! I'll look for those places!
I really appreciate your reply!

I put mine on the sea water pump housing.

I hope you do not plan on using that cheap plastic tubing.

Nope, they do not.

It looks like I will use the same location. Where would I find a better tubing? Any suggestions?

OK. Thanks anyway for your input!

The poly tubing will work fine. My current boat has the original tubing from 23 years ago and never an issue.
I replaced it on previous boat due to clogging. You just have to make sure you don't kink it when you run it from the engine to the helm.