Re: Where does the PSI gauge hook up on a 1985 75 hp Mariner
If it is a water pressure gauge, it measures the water pump pressure and there are a number of ways to connect it to the engine. One way is to simply use a "T" fitting in the tell-tale and the other is to install a hose barb fitting in the engine provided there is a port that will accept it. Here is a picture of just one way it's done on a newer 75 HP Merc. Understand however that depending on how the cooling system is designed, this technique may not work. The second picture is of the same engine, but the temperature sender occupies the water jacket port in which you insert a hose barb (if such a port is available).
"T" in the tell-tale
Hose barb in unused water jacket port