I have a '00 3cyl 2 cycle 90hp Merc OB. Being the anal gauge watcher
that I am I'd like to add a water pressure gauge.

Question is: Where does the sending hose get attached? I see on the
back of the motor is a port with a brass plug in it that looks it
gives access to the water jacket. Currently I have a auto water temp
sending unit in there. Maybe this port is opened when one wants to
drain the motor for the winter.

The other option would be on the port side of the motor is where the
tell tale hose is attached. I could put a T there and attach the
water pressure and tell tale there.

Or maybe there's really another attachment point I havent' found yet?

Question is. Do these access the same opening into the water jacket?
Any reason to use one spot versus the other? I'd like to be able to
keep water temp gauge although I could probably mount that sensor
somewhere else with some extra work.

tks
Don