My water pressure gauge is a lair!!

[mlschmitz]

Hi Fellas,

Anyone ever troubleshoot a water pressure gauge reading zero while boat is peeing strong. My quess is its not the gauge.

What are the simple checks (if any)? OEM Merc manual is silent on this topic.

My specs


Tracker by mercury 2 stroke 115hp
Model# 1115412zn
SN# ot463914

Thanks

 

[mogfisher]

Re: My water pressure gauge is a lair!!

I just diagnosed this issue on my project boat. I had found the line under the dash was disconnected going to the gauge so I hooked it up thinking it would work. NOT. So I found the connection on the motor and popped it off. On my 89 150 merc it is on the center of the powerhead towards the rear. There is a small hose that goes from there to the gauge. Really basic. With the line popped off of the head and the gauge, I used an air compressor and put air through it to verify the line was good. It was so I connected the gauge back up and sent 30 psi through the line from the powerhead. Still no movement on the gauge so it is bad. The wires to it are only for the light. Upon taking it apart (destroying it even more) I found that the assembly was just frozen. I need a new gauge. The gauge is really basic and easy to test. I tested my speedo the same way by popping off the line to the lower unit. Good luck to ya.

Adam

 

[sschefer]

Re: My water pressure gauge is a lair!!

Hi Fellas,

Anyone ever troubleshoot a water pressure gauge reading zero while boat is peeing strong. My quess is its not the gauge.

What are the simple checks (if any)? OEM Merc manual is silent on this topic.

My specs


Tracker by mercury 2 stroke 115hp
Model# 1115412zn
SN# ot463914

Thanks

If you tee'd into the pee tube to get your water pressure it may read 0 on the hose. In the water you might only show 4-6 lbs @ WOT. There should be a 1/4" plug on the cylinder cover that you can remove and take your water pressure from, it should show more pressure. It's usually up by #1 cylinder but varies from year to year and model to model.

 

[mlschmitz]

Re: My water pressure gauge is a lair!!

Thanks SSchefer

Are you saying that if the sensing line to the gauge is teed in the pee hole line then it is normal to read 4 to 6PSI, and additionally, I should move the sensing line to the plug at the cylinder?

 

[mlschmitz]

Re: My water pressure gauge is a lair!!

Thanks Adam and best of luck to you

 

[j_martin]

Re: My water pressure gauge is a lair!!

Thanks SSchefer

Are you saying that if the sensing line to the gauge is teed in the pee hole line then it is normal to read 4 to 6PSI, and additionally, I should move the sensing line to the plug at the cylinder?

That's correct. The line to the tattletale is the drain line for the t-stats, so it only gets what goes through the t-stats, and with little back pressure to boot.

hope it helps
John

 

[sschefer]

Re: My water pressure gauge is a lair!!

Thanks SSchefer

Are you saying that if the sensing line to the gauge is teed in the pee hole line then it is normal to read 4 to 6PSI, and additionally, I should move the sensing line to the plug at the cylinder?

Note that I said might and may.. It varies, some folks manage to get an accepatable reading when the gauge is tapped in at the tell tale fitting. I didnt' with my 100 Mariner so I took out the plug up by #1 spark plug and installed my water fitting there. My results were more pressure showing on the gauge and what I felt was a more accurate representation of the health of the cooling system.

 

[Silvertip]

Re: My water pressure gauge is a lair!!

Some water pressure gauges work fine when "T'd" into the tell tale and others do not. It all depends on the cooling system design and where the tell tale originates.

 

[Moody Blue]

Re: My water pressure gauge is a lair!!

I had very poor results trying to "T" into the telltale line. Read 0 at idle and only 3-5 PSI at WOT.

Moved the takeoff to the port on the head and got true readings of 2-3PSI at idle and 10-12PSI at WOT. I've got a 0-15PSI gauge so I get almost full scale readings.