Hook the psi gauges up to the oil cooler. You should have 5-8 PSI Idel and Merc says the 525 closed system is good to 43PSI IMCO's with the water pickups at the very front of the cones makes a lot of pressure but the 525 likes water pressure. The factory service manual puts the max at 43 PSI. If you see more you may have to add relief valves.

Thats where I put them. My buds fountain with 525,s have them in the oil cooler to. (way over rated boat)

Not to sound stupid but am I hooking the psi hoses up to an existing port or do I have to T it off with a fitting?

[ATTACH=CONFIG]503492[/ATTACH]

Take the merc water pressure sensor out of the oil cooler and put your hose there. (See Diagram)
http://www.boats.net/parts/search/Me...%29/parts.html

I see the diagram and I understand. When I remove the sensor is there a kit merc makes for the hook up. By disconnecting that sensor will it effect the ecu? I greatly appreciate all of the correct info, thanx tim

Some things are just not do it yourself projects. Take it to a shop and have them install the gauges.

Provided there's room, a standard T-fitting would allow you to retain your sensor and install a hose barb for your pressure line. Another alternative is to insert a t-fitting into the supply water hose (Teague and Eddie Marine sells these for larger diameter hoses). I believe Merc's pressure relief valve kit similarly installs in a hose but not sure which hose is recommended.

Drill a hole and tape it 1/4 pipe in the plate on outlet side of your oil cooler that you can remove to clean it. This way if you plug it up you know wright away. That's the first place crap gets stuck . I have done all my 500s like that . simple and done!