That yellow line is a vent line for the fuel pump diaphragm. In an automotive fuel pump, if the pump diaphragm leaks, the nipple position is just a hole, and fuel leaks out the hole. In marine applications, it is basically an automotive fuel pump with that nipple and yellow hose so the fuel...
Being an older boat, sometimes a valid course of action would be to replace items, like raw water pump impeller and the underwater rubber parts, to set a new baseline for maintenance intervals.
I pull my drive off for the winters and store in garage, so I do the checks and alignment check every...
Water pressure sensor in the line between the raw water pump and the 1st oil / PS cooler maybe?
Look on youtube and there are videos showing what to do to check / clean the port in the water line manifold.
Actually, the one it's pointing to is now #1, but that may confuse someone down the road troubleshooting a problem, if it's not like the picture.
My OCD tells me to make it like the diagrams. If it doesn't match then the dizzy needs to be reset on the cam gear.
We don't need new or to "creatively" change the border laws. Just strictly enforce the F****n one that are on the books already. You know, the ones that have been there since the early 1900's that certain folks like to ignore for political gain.