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Mercury XR4 150

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markk

New member
I have a XR4 with low water pressure about 1-2 lbs at idle and 5 at 2000-3000rpm. I have replaced the water pump, and thermostats with no avail. However when I was replacing the thermostats one of them had exhaust residue on it. I checked the bypass valve and seems to be fine again with a little exhaust residue on it. I am now thinking the exhaust manifold gasket must be bad....Any thoughts on this??? I had low to intermittent water coming out the pee hole on the back of the motor sometimes just steam and then water spurts...Any input will be appreciated running out of ideas...

Thanks,Mark
 
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Is is possible the base gasket is bad. What I do is rig a garden hose to the water pipe and turn on the hose and read the pressure. And see if water pours out the thermostat openings with the caps off.
 
I tried your suggestion, and yes water did eventually come out the thermostat holes. I did also have water coming out of the lower end also, it wasn't from the hose leaking either. I am still at at loss here though....
 
When you say "replaced the waterpump", did that include all the seals and gaskets or just a new impeller?

The intermittent water and steam indicates a shortage of water into the powerhead.

Possible causes -

clogged intake tube

bad waterpump cover gasket

bad (oil) seal in waterpump cover

bad seal where the water tube enters the waterpump cover

slipped impeller key during reassembly

hole in the water tube

bad seal where the water tube connects to the powerhead

bad powerhead base gasket

cooties and crud in the water channels/jackets (particularly in salt run motors - but dirt/sand/mud can cause clogs as well)

You need to start back at the bottom where the water is "sucked in" and work your way up systematically....
 
The water pump was a complete replacement gaskets, impeller, housing, etc. With connecting the water hose to tube on the lower unit I would say it is clear of any obstructions. My main concern is that there is exhaust residue on the thermostats and bypass valve poppet. I would think that in the power head there would not be any exhaust just water, until it returns to the lower end of the motor. Correct?
 
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Found the problem, exhaust manifold gasket...Now I just need the torque specs for the bolts to get it back together. Thanks For the help guys.....
 
I know this is an old thread but was hoping I could get the torque specs also. I found no clickable links or info on the answer.
I am a new member with a 87 ranger 373v/ 88 merc XR4. I have a leak at the bottom of my exhaust manifold/ plate divider area.
Ordered the gaskets and and divider seal. Will order divider and/or manifold if I find pitting/corrosion or missing metal where the gasket is leaking. Haven't disassembled yet but hoping it's just the outer gasket.
Thanks for any info I recieve here. Also may be looking into buying the best repair manual for this motor. I know some of these mercs changed within the same year of manufacture. Mine is 0B304074.
 
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