Water pressure gauge installation

[jdupree]

I am installing a water pressure gauge on my 1992 200hp Mercury. Just want to know if I installed the T fitting in the right place? Found the 90 deg fitting on the top of the block where I assume the water comes in? I went about 2 or 3 inches down from that and cut the hose. Installed the plastic "T" fitting that comes with the kit that joins the hose back together. I ran the water pressure hose from that. Does this sound good? Thanks.

 

[MaggieRose]

Re: Water pressure gauge installation

That is the right location for the gage tap.

 

[jdupree]

Re: Water pressure gauge installation

What kind of reading should I expect at idle, WOT for this motor? Thanks again.

 

[hkeiner]

Re: Water pressure gauge installation

My Mercury shop manual says "12 PSI Minimum @ 5500 RPM" for the 200HP. The manual does not seem to mention what the minimum PSI should be at idle. The below linked DIY article provides some more information on water pressure gauge installation. It indicates that 8-12 PSI at idle and 22 PSI at WOT is normal.

http://www.diy-boat.com/index.php?option=com_content&task=view&id=151&Itemid=49

It is often suggested to change/rebuild the water pump at the same time as installing a water pressure gauge for the first time. This way you can identify your own baseline for a "normal" reading. If you then see the PSI readings start to go above or below your "normal" reading, you know you have a water pressure problem that should be investigated and resolved.

I recently installed a water pressure gauge on my motor for the first time and I really like being able to monitor the pressure levels when using the boat. It gives me much more peace of mind than I had visually checking the pee stream from time to time or counting on the temp warning buzzer to sound off in time to avoid damage to the motor. I have not used my boat since last fall and I don't recall at the moment what the actual normal WOT reading on the gauge was. I believe it was lower than the 22 PSI suggested by the DIY article but above the minimum 12 PSI spec.
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[jdupree]

Re: Water pressure gauge installation

Thanks for the info and the link. Just re-built the water pump about 6 months ago. I don't even think that I have 10 hours on the new water pump. Looks like I tapped into the right location.

This motor tends to run on the warm side. I just think it is the "nature of the beast" with these engines. It was just re-built 2 seasons ago with all the cooling components replaced. I was just looking for some "piece of mind" as far as the water pump goes. Thanks again!

 

[hkeiner]

Re: Water pressure gauge installation

I also installed a temp gauge on my boat. The motor already had an OEM temp sending unit installed on the port side and all I had to do is route a send wire to the dash and install a temp gauge. The sender measures water temp and the gauge normally shows about 150 degrees at idle and about 130 degrees at WOT. There is some lag, of course, between the change in motor RPMs and what the temp gauge shows. This is another thing that helps my peace of mind. I need the peace of mind because if I blow up this motor, I can't easily afford to replace it.

 

[MaggieRose]

Re: Water pressure gauge installation

Pressure at idle should be around 3 psi. A PRV located at the bottom of the powerhead on the starboard side should regulate the pressure around 12-15 psi at WOT.

 

[jdupree]

Re: Water pressure gauge installation

Pressure at idle should be around 3 psi. A PRV located at the bottom of the powerhead on the starboard side should regulate the pressure around 12-15 psi at WOT.

It looks like that is correct. I am showing around 2 psi running it in the yard with the hose hooked up. I expect it will be 3 to 4 psi in the water. Water pump is brand new. Anyone else showing this reading at idle?

 

[gss036]

Re: Water pressure gauge installation

2 psi -- 12 psi is the normal range. The stats open at about 143 degrees. So running 150 at idle would be acceptable and WOT with the poppet valve open it will probably run considerably cooler and may progress up a little bit on a long run- 20-30 minutes.