1984 Mercury V-6 150HP Poppet Valve

J

JimDD

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I have an antique 1984 Mercury V-6 that has its overheat alarm come on at around 3000 rpm. Water pump is less than two years old and at idle water gauge ~3-5 psi, higher rpms pressure runs 15 psi +.

I have maintained this engine myself for the past years since I bought it new in '84. I had corrosion erode the area where the original poppet valve two round housings fit, so I replaced the older design poppet members with one figure 8 design. The fig. 8 part came off of a parts engine of a friend.

Could the spring tension behind the fig. 8 part be weaker than the original spring tension, and possibly be prematurely dumping more water into the exhaust and not up the powerhead through the therms etc. causing my overheat?

Much appreciate any thoughts or help anyone could provide.

Thanks!
 
C

Chris1956

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I believe the poppit valve, when open at 2000RPM or so, dumps water into the engine to cool it. The thermostats are therefore bypassed when the poppit opens.

I do know that the poppit valve design has changed over the years. You might get original parts for yours to assure it works correctly.
 
sam am I

sam am I

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JimDD said:
I have an antique 1984 Mercury V-6 that has its overheat alarm come on at around 3000 rpm. Water pump is less than two years old and at idle water gauge ~3-5 psi, higher rpms pressure runs 15 psi +.

I have maintained this engine myself for the past years since I bought it new in '84. I had corrosion erode the area where the original poppet valve two round housings fit, so I replaced the older design poppet members with one figure 8 design. The fig. 8 part came off of a parts engine of a friend.

Could the spring tension behind the fig. 8 part be weaker than the original spring tension, and possibly be prematurely dumping more water into the exhaust and not up the powerhead through the therms etc. causing my overheat?

Much appreciate any thoughts or help anyone could provide.

Thanks!
Click to expand...
It's possible, sure......... I'd suspect the springs when manu'd all have same'ish tension constants and are probably then by default, opening at the same fixed'ish pressure point, and yes, when opened dump excess pressurized lake water directly back into the exhaust as to not over pressure the block. Still got your old spring? Maybe the old replacement you swapped in had just lost some of it's tension (maybe only needs to be off as much as 10/20%, IDK) Switch'um see if anything changes eh?

Spring's are pretty linear up to a point, you could set both side by side and place a weight(same, few oz's etc) on each, in turn and measure the deflection distance for each with calipers.......That'll tell ya if their off from one another if the distance's vary.
 
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Dukedog

Dukedog

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has tha poppet ever been serviced/replaced?.. why not start with a NEW poppet assembly???.. not that expensive.. if ya have some minor "pitting" a little JB and time (elbow grease) will do tha job of filling marks in.

some of tha guts made a slight change over tha years but in all of 'em tha spring remained tha same
 
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J

JimDD

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Jul 28, 2009
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Dukedog said:
has tha poppet ever been serviced/replaced?.. why not start with a NEW poppet assembly???.. not that expensive.. if ya have some minor "pitting" a little JB and time (elbow grease) will do tha job of filling marks in.

some of tha guts made a slight change over tha years but in all of 'em tha spring remained tha same
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I believe I will have to rebuild the original surface with JB and rebuild the original design with the two round members as originally installed. Thanks, and take care Dukedog!
 
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