Hello: I added a water pressure gauge to my 2004 Merc. 90. I bought the kit on ebay. It was the Faria brand , a 2 inch gauge . around $50.00 . It has a thin water line going to the gauge . It is a 30 psi gauge . I don't know anything about a temperature gauge . I thought if I have water pressure I'm good to go . With a water pressure gauge you know that your still good to go even though you have a plugged pee hole. Good Luck . O - R