Mercury XR6 Water Pressure TOO HIGH

[mattsmechanical247]

Hello, I am sort of new to working on outboards but I am getting the hang of it quickly. I am working on a 2003 Mercury XR6, I have replaced the thermostats, rebuilt the poppet valve, and installed a new water pump impeller and upper housing. The motor starts, runs and smokes just as it should but at idle I get anywhere from 10 - 20 PSI of water pressure and at WOT it pegs the gauge I installed past 30 PSI. At first, I didn't know this was a problem so I ran the boat at the lake and quickly got a warning buzzer that was telling me the motor was overheating. Talking to some guys at the shop near me, they told me that I should get 3-6 PSI at idle and 10-20 at WOT, and my motor is overheating because the water pressure is too high. They also told me that it is probably due to a blockage at the base of the motor from the exhaust plate gasket. I would like to exhaust all possible options before I pull the motor and replace this gasket. Thanks for your help!

 

[Dukedog]

like said, ya gotta "blockage somewhere"... more than likely where they said but could actually be anywhere, in any water passages, anywhere in tha motor......

 

[sam am I]

MOUSE!!! ...........J/K!!!

http://biggerhammer.net/mercury/wate...5_blizzard.jpg

If your block is similar (might look for/need a drawing like or similar if your motor differs too much) and depending of where your H2O gauge is plumbed in, I'd think from a trouble shooting/diagnostic standpoint, you could start by removing the thermostats and/or poppet, fire it up and see what happens (pressure SHOULD drop and it SHOULD run cool/cold)....

Off the cuff, it sounds sorta poppet valve issue, they do crack open at an idle and reg the pressure, mine does anyway, not sure how much tho. I have clear hoses throughout my motor, looks like a big crazy straw when I fire it up and.......

My (all?) poppet hose (controls the opening of the poppet) does have some flow at an idle which implies the valve is opening (how much needs to be there? IDK, enough to overcome the spring's force on the valve I presume. Perhaps someday I should data log that), which implies some pressure relief (how much? IDK, another to do list item)....perhaps start there.

Let us know what ya find from that, if we can't figure it out, we'll sure make something up

 

[sam am I]

A quick addition/correction FWIW if applicable to the above ^^ statement of "My (all?) poppet hose (controls the opening of the poppet) does have some flow at an idle which implies the valve is opening".

After further review of some additional details...........The poppet control tube/hose can have flow into the poppet assembly and the poppet valve can still be completely closed!!.....Apologies

 

[mattsmechanical247]

Thanks for the responses, I pulled the exhaust motor and exhaust plate yesterday and there was heavy calcium build up but it all just flaked out and didn't seem to be in any water passages. My shop ordered me new gaskets and also suggested I change the exhaust manifold cover gasket because an exhaust leak will cause high high pressure and overheating. Where do you get clear hoses, that might be kind of cool?

 

[sam am I]

FT-Tygon-LP1500.pdf

Get it at like............

http://www.usplastic.com/catalog/ite...0254&catid=864

Good stuff and tough as nails!!.......It's a lil low on the high temp side (185F) but OB's typically run 150/160'ish on the norm, all is fairing well in my engine so far, going on 3 seasons with it........It's also E-10 safe :facepalm:

Aside from cool....I particularly like it as I can pop the hood and can easily/quickly at a glance spot check for like air bubbles in fuel, proper'ish flow in water lines, bleeder flows, oil in mix lines etc., etc. I can even see the engine's gas vapor moving back and forth in the line that runs the fuel pump's diaphragm....

Once you get a visual base line on what things are suppose to look like when the engine is running properly.....Then it's just a quick visual at things when you pop the hood before that hot date on the lake.....Don't want unexpected engine issues now do we?

 

[mattsmechanical247]

Well, I think I have figured it out, I pulled the lower exhaust plate and the "diffuser" or exhaust tubes were completely disconnected from the plate. Two of the bolts were gone and the other two were broken. because this tube was rattling around in the big chamber. it put two holes in it. So I have ordered all news studs, nuts, and gaskets, and I am working on getting the holes repaired. Hopefully, this was the cause of my high water pressure and overheating.