496 HO closed cooling, I installed water pressure gauges and they have machinical sender, you know the plastic tubing to the gauge. I installed it on the motor and don't get a reading on the gauge while the engine is running with water hose attached and engine at operating temp. Have I got it installed wrong? Do you have to bleed the line to the gauge? I installed the plastic tubing on the front starboard side of the engine below the heat exchanger. I was told to install it on the back of the engine on the oil cooler but my cooler has no place to mount anything, it just has 2 oil lines and a in and out water line. I was told to remove the sender from the oil cooler and install a T. There is a sender back there but it is on the manifold not the oil cooler. On the diagram below I installed the tubing to #6 plug. See red arrow.

It looks like you may have installed it in the closed cooling system and not in the seawater cooling system. The reason they have you install it in the power steering cooler is that is part of the seawater system. Yours may not have a pressure sensor on the cooler, on earlier 496's they were mounted on the outlet side of the seawater pump. Personally, I think I would have just installed a Smartcraft gauge to monitor water pressure (and other things) .

I just installed a new dash with Monsters is why I don't have the smartcraft gauge.

recheck for a bung on the bottom side of the cooler. if none then install on the outlet side of the raw water pump as said above. you should see the pipe plug on the side.

I tested it again but still no pressure with just a water hose, I'll see if it works in the water. Here is where I inst
alled it.

Theres already a sensor on the Sea water pump item #12, I dont know what it takes to get a reading from it but its range is 0-100 psi. I guess you could put a tee there one for the smartcraft sensor and the other to your gauge.

That is exactly what I did. Hope it works

Not familar with closed cooling, but my regular cooling won't show any pressure on the hose at idle rpms.

I had the same engines in my old boat and if I remember correctly I never did see water pressure gauge move when it was on the hose. The only time it moved was when it was under way.

Someone told me when you get up to 10 to 20 mph you will see pressure but very little at idel 2 to 3 psi, and none with hose. Thanks