2001 V6 2.5L 140HP Mercury running hot

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CharlieB

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Re: 2001 V6 2.5L 140HP Mercury running hot

Have you disassembled and inspected the poppet assy yet?

If the seat is warped or loose it may bind and restrict the poppet from opening smoothly at rated pressure, cutting the spring will not necessarily cure at poor fitting valve and seat.
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

Yes I have pulled the poppet assembly apart and it all looks good. I can't really fault it at all. I have ordered new gaskets, a grommet, and a carrier. I've also ordered a new spring in case the current one isn't the correct one.

There are two holes in the block. One the carrier and grommet go into that the poppet valve seals against (I guess this is where the pressure acts on) and a slot at the 6 - 9 o'clock position. Where does the slotted passage come from/go to?

Questions....

1, Where does the poppet valve sense the pressure from? Behind the valve or from the top of the block via the hose?
2, Should I also be replacing the diaphragm or any other parts?
3, What's likely to cause it to pop open at higher pressure? Nothing looks to be causing this as all the parts look to be in good condition and the valve moves freely inside the grommet.
4, Where does the water flow when the poppet is closed/open and what is the function of this slot?
5, I'm picking up the pressure from the grey tube the exits the engine below the CMD plate. Is this correct?

Sorry for the long winded post but the more I look at the poppet assembly I can't really fault it.
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

Anyone? Even if you can only answer one question?
Some of the poppet valve parts have arrived and I'm not sure if I should install them or replace more.... See above.
 

j_martin

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Re: 2001 V6 2.5L 140HP Mercury running hot

Yes I have pulled the poppet assembly apart and it all looks good. I can't really fault it at all. I have ordered new gaskets, a grommet, and a carrier. I've also ordered a new spring in case the current one isn't the correct one.

There are two holes in the block. One the carrier and grommet go into that the poppet valve seals against (I guess this is where the pressure acts on) and a slot at the 6 - 9 o'clock position. Where does the slotted passage come from/go to?

Questions....

1, Where does the poppet valve sense the pressure from? Behind the valve or from the top of the block via the hose?
2, Should I also be replacing the diaphragm or any other parts?
3, What's likely to cause it to pop open at higher pressure? Nothing looks to be causing this as all the parts look to be in good condition and the valve moves freely inside the grommet.
4, Where does the water flow when the poppet is closed/open and what is the function of this slot?
5, I'm picking up the pressure from the grey tube the exits the engine below the CMD plate. Is this correct?

Sorry for the long winded post but the more I look at the poppet assembly I can't really fault it.

1. Yes
2 & 3 Wouldn't hurt to replace the diaphragm. Sounds like you have a seat problem or wrong spring. It should open up earlier than that.
4. Other restricted ports in the base plate let the water get into the mid with the exhaust. T-stats feed into the exhaust at the base plate. Slot at the bottom of the poppet valve port feeds to the mid when the poppet opens.
5. Don't have any idea what a CMD plate is. Pressure has to be coming from the threaded hole in the top of the block just aft the flywheel. If there's a hose on it, you can T into that hose.

If you have a frankenmerc, it's possible the base plate is wrong.

hope it helps
John
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

1. Yes
2 & 3 Wouldn't hurt to replace the diaphragm. Sounds like you have a seat problem or wrong spring. It should open up earlier than that.
4. Other restricted ports in the base plate let the water get into the mid with the exhaust. T-stats feed into the exhaust at the base plate. Slot at the bottom of the poppet valve port feeds to the mid when the poppet opens.
5. Don't have any idea what a CMD plate is. Pressure has to be coming from the threaded hole in the top of the block just aft the flywheel. If there's a hose on it, you can T into that hose.

If you have a frankenmerc, it's possible the base plate is wrong.

hope it helps
John

1, Yes? Behind the poppet?
2 & 3, I've got a new diaphragm and it looks to be no different than the original one but I'm replacing it anyway.
4, It looks like water can flow from the top of the block, through the hose to the poppet housing, through it then into this slot even when the poppet valve is shut??? This doesn't sound right? But that's how it looks. Is this right?

5, The CMD plate is the plate that has all the coils attached to it. At the bottom of the block below the bottom of this plate there is a fitting that has a 4mm grey hose coming out of it for a water pressure sensor. This is where I'm sensing the water pressure to trouble shoot the poppet valve. Is this OK or not? I'm working on the hydraulic principle that says pressure is equal in all areas of an enclosed system. Or something like that.

Thanks John for all your help and advise so far.
 

j_martin

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Re: 2001 V6 2.5L 140HP Mercury running hot

1. The hose to it affects the operation. The poppet valve itself meters water from inside the block to the triangle shaped hole in the bottom of the poppet port, leading to the mid.

4. Don't know for sure. Some versions don't have a hose. I suspect pressure on this hose modifies the operation of the poppet.

5. Never seen a pressure meter connection there. All I have seen have been to the top of the block. Might be OK, just don't know.
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

1, Thank you
2, I thought as much
3, I'm going to "T" into the top hose and check the poppet operation there just in case the pressure here is different.

I'll report back once I've got back on the water. Once again the weather here sux! So much for summer!
 

j_martin

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Re: 2001 V6 2.5L 140HP Mercury running hot

1, Thank you
2, I thought as much
3, I'm going to "T" into the top hose and check the poppet operation there just in case the pressure here is different.

I'll report back once I've got back on the water. Once again the weather here sux! So much for summer!

Quit Complaining.
nutz.jpg
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

LOL! You won't be having any overheating issues in that!
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

Just looking at the passages at the poppet valve and I need this clarified?..

The hose from the top of the block feeds into the poppet assembly between the diaphragm and the block and connects with the slot shaped passage. These two sources must have the same pressure present and therefore allow little, if any, water flow at low pressure when the poppet is shut. When the pressure builds to the point that there is enough force on the diaphragm to overcome the spring pressure the poppet valve is lifted by the diaphragm away from the poppet seat (grommet and carrier) allowing water to flow into the hole/passage behind the poppet valve. This allows extra water to flow into the exhaust area which provides the extra cooling necessary to stop things melting and at the same time allows more water to flow through the P/H to keep this cool.

Is this right or have I got it completely cocked up?
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

I'd still like an answer to the post above. If someone could help that would be great.

Right.... Back on the water yesterday and same old problem. New poppet installed and its still running hot at anything over a fast idle until the poppet opens. Before it was opening at 4200 revs with 16psi, now its opening all over the place, but at lower revs and pressure. Sometimes it opens about 10 psi at about 2500 but the next time it 14 or so at over 3500? I don't get it??? At least now the poppet opens gradually rather than popping open like it did.
Pressures are:
Idle 1-2
1000 4
1500 7.5
3000 All over the place
3500 6.5

Any idea or should I reduce the poppet spring tension with the side cutters?
 

j_martin

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Re: 2001 V6 2.5L 140HP Mercury running hot

The poppet should "pop" at about 3000 rpm and at a higher pressure. The fact that it's bouncing, and the engine is hot before the poppet opens indicates lack of sufficient water flow.

Could be simply low water pressure from bad water pump parts, sucking air below the water pump, bad riser pipe or seals, etc.

I wonder if it's possible you got a LU with a high volume pump on a high pressure system. Check the official mercury parts list to check that out.
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

I'm pretty sure the pump in this thing is the typical one found in these years. i.e. low volume, high pressure. When it was replaced 4 hours ago they used a Sierra kit, not the Quick Silver one. I guess the next thing is to pull the LU and check the water pump?
 

Sumpi

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Re: 2001 V6 2.5L 140HP Mercury running hot

I have been having the same overheating problem in a V6 200 EFI and just took the boat out on the water after looking at the pressure readings in these links.
I changed the thermostats as it was an easy and cheap process. No Improvement.
At 800 RPM I get 1 PSI, 1000RPM 2 1/2PSI, 1500RPM 4 PSI, 2500RPM 11PSI, 3200RPM 15PSI, Poppet valve opens at 3500RPM around 16PSI.
The most important item that everyone is missing is that it is not the RPM that opens the Poppet valve. It is the pressure at +/- 16PSI. So if you only get 16PSI at 3500RPM then the water pump is not creating enough pressure either by blockage to the pump or the pump is in need of replacing.
I think the pump should reach 16 PSI at 2200RPM. Hence the poppet valve opens at lower revs bring in the cooling effect at lower revs.
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

Sumpi Yes it's pressure not engine speed that opens the valve. Check out the link in post #7, it shows the pressure required to open the poppet is only 9psi. Due to this lower pressure it obviously requires less revs to reach this pressure so the valve opens providing more cooling at lower revs.

I cut the spring a lot (about 2 coils) a year ago but it still runs hot. I've just replaced the water pump so I'm forever hopeful this will help. During last summer it was opening at 12psi which occured at about 33-3500rpm and the pressure dropped to about 6psi. Dropping revs the pressure remained there until about 2900 when it climbed back to 10ish. The water temp followed suit and was soon 1/2 way between 3/4 and full on the gauge. The Merc mechanics here are stumped too.

Anyway this is just an update. I'll get back on the water soon and with luck the new pump will have helped.

Merry Xmas to you all.
 

CharlieB

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Re: 2001 V6 2.5L 140HP Mercury running hot

We should have asked you a couple more questions long ago.

Did you purchase this motor with this problem or has this heating problem developed while you operated this motor?

Has this motor ran in shallow water? Could it have sand picked up and inside the motor, have you tried dropping the LU and back-flushing the motor thru the T-stat openings?

Have the cyl heads been milled to increase compression? What is the compression? What fuel are you using?

WOT timing may be too high at 26, this may be fine only at WOT but at lower throttle could be too much advance. Heating can be caused by either too much advance OR too much retarded timing. 26 at WOT does seem high, most V6's like to be in the range 21 to 23 at WOT and a small gap between the throttle roller and carb linkage to allow a few degrees advance just before the carbs open.

Try 23 and see if that makes a noticeable difference in part throttle temps.
 
M

Maxz695

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Re: 2001 V6 2.5L 140HP Mercury running hot

Does this engine have a water pick up tube from the water pump to the base? I just replaced my exhaust adapter gasket that was leaking hot exhaust onto the water tube gromet housing and somewhat melting it. If this is the case the gromet for the water tube may also be melted cracked or distorted and therefore losing some water pressure. If the engine appears to sound louder than it is expected to then that is a good sign the gasket is blown. I realize this is not a 140 HP but here is a few pics of what a leaking exhaust can do View attachment 177305View attachment 177306View attachment 177307 The housing is somewhat melted although I had changed the gromet not long ago.I just put on a new exhaust adapter gasket. My engine was running louder than it should have been. Heat can stiifen the gromet and crack it or just burn it totally up. Just something you might consider if your engine has this type of system. Only an opinion that is a possibilty.
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

We should have asked you a couple more questions long ago.

Did you purchase this motor with this problem or has this heating problem developed while you operated this motor?

Has this motor ran in shallow water? Could it have sand picked up and inside the motor, have you tried dropping the LU and back-flushing the motor thru the T-stat openings?

Have the cyl heads been milled to increase compression? What is the compression? What fuel are you using?

WOT timing may be too high at 26, this may be fine only at WOT but at lower throttle could be too much advance. Heating can be caused by either too much advance OR too much retarded timing. 26 at WOT does seem high, most V6's like to be in the range 21 to 23 at WOT and a small gap between the throttle roller and carb linkage to allow a few degrees advance just before the carbs open.

Try 23 and see if that makes a noticeable difference in part throttle temps.

When I bought the boat/engine this heating issue wasn't mentioned yet I'd bet a years salary it was one of the main reasons the guy sold the boat.
As it's 3rd hand it could have sucked up a load of sand. I have back flushed it (LU still attached tho) and everything seems OK.

I doubt the heads have been off the motor as it only had 75 hours on it when I got it and the condition of the PH suggests it hasn't had much done to it. Looks to even have the original plugs in it. Fuel is local 91.

When I checked the timing there was a large gap between the roller and carb linkage. I adjusted this to zero some time ago. The changes I've made to date have so far all helped but I'll have a play with the timing to see how that goes.

The motor runs great but it seems that according to the table mentioned in post #7 that the poppet should open at a lower pressure than it is. It was 16psi now I've got it down to 12 but it still needs about 3200rpm to achieve this.
 

McHaggis

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Re: 2001 V6 2.5L 140HP Mercury running hot

Does this engine have a water pick up tube from the water pump to the base? I just replaced my exhaust adapter gasket that was leaking hot exhaust onto the water tube gromet housing and somewhat melting it. If this is the case the gromet for the water tube may also be melted cracked or distorted and therefore losing some water pressure. If the engine appears to sound louder than it is expected to then that is a good sign the gasket is blown. I realize this is not a 140 HP but here is a few pics of what a leaking exhaust can do View attachment 177305View attachment 177306View attachment 177307 The housing is somewhat melted although I had changed the gromet not long ago.I just put on a new exhaust adapter gasket. My engine was running louder than it should have been. Heat can stiifen the gromet and crack it or just burn it totally up. Just something you might consider if your engine has this type of system. Only an opinion that is a possibilty.

Yes it does have a tube. Not sure if it louder than it should be but it sounds OK. Exhaust entering the water system was mentioned at some stage but they said the likely area was at the water pump. All good in that area but you might be on the right track. The tell tale can be a bit spitty at times like there's air in it???
 

CharlieB

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Re: 2001 V6 2.5L 140HP Mercury running hot

Removing the LU to back-flush thru the stat openings will allow a much greater flow volume than with the LU in place.

Next time you have the LU down give it a try just to be sure.

Also, when the lower is down rig a garden hose directly to the water transfer pipe, if it fits well you may be able to look up to the upper end of the pipe's fit in the grommet in the adaptor plate to see if it is leaking or well sealed as it should be.
 
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