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mercury 2+2 check valves

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Mattc8821

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have an 03 Mercury 125 2 stroke. 2+2

These motors have 2 check valves that are connected to fuel lines that seem to run from the accelerator pump.The check valves screw into the block- one screws into where cyl 3 is located, and another right below into cylinder 4.

Can someone tell me what issues it would cause if one of these check valves was faulty?
 
Anyone?

been having issues with my motor not running on #4 cyl. If the #4 Check valve is bad, would it prevent that cylinder from getting fuel?
 
No it would not.----First explain what trouble shooting if any has been done ?----Compression tested ?----Checked for strong spark ?------Made sure carburetors are clean ?-----Fuel pump diaphragm looked at.------Of course you know that the bottom 2 carburetors do not put any fuel into the motor at idle and below 1800 RPM.
 
racerone said:
No it would not.----First explain what trouble shooting if any has been done ?----Compression tested ?----Checked for strong spark ?------Made sure carburetors are clean ?-----Fuel pump diaphragm looked at.------Of course you know that the bottom 2 carburetors do not put any fuel into the motor at idle and below 1800 RPM.
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i posted about this before but still didn't figure it out. Here's info below:



2003 Mercury 125 Saltwater 2 stroke (2+2) on 20ft dual console
Boat only getting up to about 4200rpms and 30mph according to gps
Compression 120+ in all 4 cyls
I've determined that it's not running on the #4 cylinder. When I pull that plug wire off, it gets up to the same speed / rpm as if it's plugged in. When I run it and pull the spark plug, it looks a little wet, but there's no color on the plug at all, as if I just took it out of the box. Changed spark plugs around to rule out getting bad plug.


Cylinder is getting spark. I have a spark light and have spark gap tester. Set gap to 7/16 and spark jumps that gap. Spark light lights up when running. Hooked up timing light and it also read same rpms as other 3 cylinders at idle.


Pulled off carb and went through it 3 times. I'm about 100% sure that there are no obstructions in carb. Got rebuild kit also, so needles are new. Float height good also. I even switched floats and needle between carb 3 and 4 to make sure float height wasn't issue, and it wasn't. Still wasn't running on #4. Also primed bulb and unscrewed drain screw on bowl to make sure fuel was in it, and it was.


Thought it maybe wasn't sucking fuel. Pulled reeds out and reeds are 100% perfect. Put my hand over carb when running and felt suction. It also drew some fuel out of the bowl when covered. I also have a steamer - I put steam in front of each carb and had someone crank motor and watched it suck steam into each carb. So suction seems good. Also rebuilt fuel pump.


Had boat on the water and up to around 3500rpms. I sprayed some fuel into that #4 carb and there was no change in speed or rpms.


Regulator is brand new. Trigger is brand new. Stator tested good with meter -did testing procedure in manual. I unhooked rev limiter and ran it and made no difference. I swapped cdms around and ran it which also made no difference. I also traced each wire for each plug that plugs into cdm module and tested continuity on each one, and all wires seem good.


My next thought was that maybe there was some water getting into that bottom cylinder. Maybe that's why the spark plug looks brand new when I pull it out because steam is cleaning it. Maybe plug looks a little wet when I pull it from water or steam. If I run it in driveway and pull out that spark plug after I shut it down, steam does come out of that spark plug hole. Not sure if that's normal or not. Also read that water intrusion will steam out a cylinder will not let it fire even if there's spark.
I pulled the exhaust side cover off of motor and replaced that gasket / water jacket. Thought maybe some water could get into cylinder from exhaust port area . But I ran it this morning and still only getting around 4-4200rpms. These motors seem simple but this is throwing me for a loop


The strange part about my run this morning was that when I first put it in and ran it, my tach said it was hitting 5000 rpms which it hasn't done since this issue began. But gps speed was still saying around 30mph. It didn't feel like it was going as fast as it should be, even though rpms were reading higher. So I pulled that plug wire off and ran it again and rpms only went up to 4200, still around 30mph. I reconnected that plug wire and ran again. Speed still around 30 and rpms stayed at 4200, not 5,000.
 
I'm no mechanic but isn't steam coming out of that cylinder's spark plug hole a clue? Does steam come out of any other plug holes?
 
RickM46 said:
I'm no mechanic but isn't steam coming out of that cylinder's spark plug hole a clue? Does steam come out of any other plug holes?
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That was my thought, but I replaced the gaskets under exhaust cover and also water jacket on back and it hasn't made a difference
 
RickM46 said:
I'm no mechanic but isn't steam coming out of that cylinder's spark plug hole a clue? Does steam come out of any other plug holes?
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There was some mention of possible bad high speed winding in stator. Tested stator with multimeter and followed cdi electronics website. Ohms read fine, but I'm not sure if that would tell me whether or not the high speed was good or not. I had a mechanic tell me that the bad check valve in that cyl was most likely going to be my issue , but just don't see how that bad valve could restrict fuel from getting into that cyl from the carb
 
You dont have a high speed side if you have CDM modules. The check is actually a simple injector that increases pressure squirt from accelerator pump. You have either low compression, water intrusion from lower seal or a reed problem
 
faztbullet said:
You dont have a high speed side if you have CDM modules. The check is actually a simple injector that increases pressure squirt from accelerator pump. You have either low compression, water intrusion from lower seal or a reed problem
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Compression close to 130 and I took reeds out to inspect and they are perfect. What would the lower seal be?
 
Well after cleaning out bad check valve connected to cylinder 4 this has fixed my issue! Saw 5200 rpms today for the first time since getting this boat. Spark plug color looks good.
 
That makes no sense as the valve only adds fuel when accelerator pump is pushed. This activates bottom cylinders when planning, once throttle is past 1/4 the circuit in carb takes over and check valve is no longer in fuel circuit as accelerator pump is empty..
 
I don't really get it either. But I feel like I've done every test possible to figure out what was going on with this thing. That bad check valve was the first thing I found that was wrong that related to the cylinder that was acting up. :confused:
 
Mattc8821 said:
Well after cleaning out bad check valve connected to cylinder 4 this has fixed my issue! Saw 5200 rpms today for the first time since getting this boat. Spark plug color looks good.
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I have a 2000 125HP with similar issue. Only get 4300 RPM/32 MPH.
It could that the propeller is too big, and/or the outboard is mounted too low, but since this solved your issue when doesn't make sense, it is well worth it to give it a try.
Where exactly are these 2 valves located?
I'm assuming on the stardboard side, because I don't remember seeing them on the port side or the rear.
Thanks in advance.
 
flcusat said:
I have a 2000 125HP with similar issue. Only get 4300 RPM/32 MPH.
It could that the propeller is too big, and/or the outboard is mounted too low, but since this solved your issue when doesn't make sense, it is well worth it to give it a try.
Where exactly are these 2 valves located?
I'm assuming on the stardboard side, because I don't remember seeing them on the port side or the rear.
Thanks in advance.
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They are on the starboard side. I removed the mounting plate that holds the CDMs. The two check valves are screwed right into the block behind that plate. I unscrewed them from the block , sprayed some carb cleaner into each end. On the bad one, carb cleaner came out of both opposite ends , when it should only come out of one end. You can unscrew the check valves and clean out the inside of them. There's nothing but a spring and a needle with rubber tip inside. But I just bought a new one and replaced. Really didn't make a lot of sense how one of these being held open could prevent a cylinder from firing, but it did somehow.
 
Did you replace the two small filters that feed the check valves. Make sure your engine has them. Mine are 1995 (twin 115's) but they changed the check valve feed system in 1996. When I replaced mine they were full of debris, I cut them in half and they were stuffed.
 
fitz73222 said:
Did you replace the two small filters that feed the check valves. Make sure your engine has them. Mine are 1995 (twin 115's) but they changed the check valve feed system in 1996. When I replaced mine they were full of debris, I cut them in half and they were stuffed.
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Yes good to check. I checked both of mine and they were clear .
 
Mattc8821 said:
They are on the starboard side. I removed the mounting plate that holds the CDMs. The two check valves are screwed right into the block behind that plate. I unscrewed them from the block , sprayed some carb cleaner into each end. On the bad one, carb cleaner came out of both opposite ends , when it should only come out of one end. You can unscrew the check valves and clean out the inside of them. There's nothing but a spring and a needle with rubber tip inside. But I just bought a new one and replaced. Really didn't make a lot of sense how one of these being held open could prevent a cylinder from firing, but it did somehow.
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Thanks for answering my question. I will check them and make sure they are working properly.
 
fitz73222 said:
Did you replace the two small filters that feed the check valves. Make sure your engine has them. Mine are 1995 (twin 115's) but they changed the check valve feed system in 1996. When I replaced mine they were full of debris, I cut them in half and they were stuffed.
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I wasn't aware that were any more filters other than the one after the accelaration pump. I'll check those as well.
 
fitz73222 said:
Did you replace the two small filters that feed the check valves. Make sure your engine has them. Mine are 1995 (twin 115's) but they changed the check valve feed system in 1996. When I replaced mine they were full of debris, I cut them in half and they were stuffed.
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In the 2000 engine (at least on the service manual) there is just one filter after the acceleration pump, then after the filter there is a T fitting to one valve and after that T another T to the second valve and out of that T to the main fuel line input
 
flcusat said:
What's your top speed now at 5200 RPMs?
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Ive had it out twice sinced fixing. Both times had 4+ people in the boat, but getting over 35mph at 5200 with that many people. Before I was getting like 28mph at like 4200.

My second filter is behind my oil tank on starboard side of motor. Filter is a small one.
 

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Mattc8821 said:
Ive had it out twice sinced fixing. Both times had 4+ people in the boat, but getting over 35mph at 5200 with that many people. Before I was getting like 28mph at like 4200.

My second filter is behind my oil tank on starboard side of motor. Filter is a small one.
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Thanks for the reply.
My setup is identical to yours regarding the filters.
Main filter inside the outboard is in between the fuel pump and carburetors, and the second smaller filter after the acceleration pump feedingthe check valves.
Another question what size of propeller are you running?
I'm running a 13 x 18 and getting 32 MPH at WOT, but only getting up to 4300 RPM. My outboard is mounted all the way down, so I was assuming that the RPM issue was either the propeller, the motor height or a combination of both. Then I found your post and I though it was worth it to give it a try, since it was the more affordable choice out of the three, and go from there.
 
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I took out both check valves this morning.
My first impression was that they there were both clogged.
I try blowing with my mouth in the direction of flow and couldn't open the valve. I don't know if the pressure put out by the acceleration pump is greater than what i can put with my mouth, but I didn't want to blow it with the compressor.
Then I tried with a carburatr cleaner spray, and it took several tries before the valves will open and let the flow through it.
I openened them up, and put all the parts except for the actual actuator with the rubber tip in Gunk Carburator cleaner. I will leave them there for 24 hours and then reasemble and test again.
Originally I was thinking on replacing them with new ones, but the rubber tips looked pretty good, and man this pieces are expensive at around $50 each, so I decided to give it a good clean first and see how that goes.
I'll keep you guys posted.
 
flcusat said:
I took out both check valves this morning.
My first impression was that they there were both clogged.
I try blowing with my mouth in the direction of flow and couldn't open the valve. I don't know if the pressure put out by the acceleration pump is greater than what i can put with my mouth, but I didn't want to blow it with the compressor.
Then I tried with a carburatr cleaner spray, and it took several tries before the valves will open and let the flow through it.
I openened them up, and put all the parts except for the actual actuator with the rubber tip in Gunk Carburator cleaner. I will leave them there for 24 hours and then reasemble and test again.
Originally I was thinking on replacing them with new ones, but the rubber tips looked pretty good, and man this pieces are expensive at around $50 each, so I decided to give it a good clean first and see how that goes.
I'll keep you guys posted.
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Running 17p prop.

Yes those check valves are crazy expensive for what they are. Something to keep in mind::

after I reinstalled check valves after cleaning, i would prime ball and it wasn't getting completely hard. Like I could keep squeezing it and I could hear fuel still moving around in the motor somewhere. Ran boat and bulb was getting soft / motor wanted to die from starvation. I got home and I took out both of those check valves again. I reconnected the fuel lines to them while they are unscrewed from the block and I squeezed primer bulb. When squeezing it pretty softly, there was fuel coming out of that #4 check valve . It should take a certain amount of pressure to open up that valve to let fuel into motor. I had to squeeze a lot harder for fuel to squirt out of #3 check valve. This test showed me that the #4 check valve wasn't performing as it should. I did replace that one with a new one. Now primer bulb stays hard, and boat runs perfect.
 
Mattc8821 said:
Running 17p prop.

Yes those check valves are crazy expensive for what they are. Something to keep in mind::

after I reinstalled check valves after cleaning, i would prime ball and it wasn't getting completely hard. Like I could keep squeezing it and I could hear fuel still moving around in the motor somewhere. Ran boat and bulb was getting soft / motor wanted to die from starvation. I got home and I took out both of those check valves again. I reconnected the fuel lines to them while they are unscrewed from the block and I squeezed primer bulb. When squeezing it pretty softly, there was fuel coming out of that #4 check valve . It should take a certain amount of pressure to open up that valve to let fuel into motor. I had to squeeze a lot harder for fuel to squirt out of #3 check valve. This test showed me that the #4 check valve wasn't performing as it should. I did replace that one with a new one. Now primer bulb stays hard, and boat runs perfect.
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Thanks for the heads up. I'll definately will check the valves with the primer bulb before putting them back in to the block.
Now analizing what you are saying, it looks like the acceleration pump is open while in iddle, providing a little fuel to the bottom 2 cylinders for lubrication and once the accelerator pump is activated with the throttle arm, it closes the flow to the check valves and the carburators are taking over. it is this correct?
 
flcusat said:
Thanks for the heads up. I'll definately will check the valves with the primer bulb before putting them back in to the block.
Now analizing what you are saying, it looks like the acceleration pump is open while in iddle, providing a little fuel to the bottom 2 cylinders for lubrication and once the accelerator pump is activated with the throttle arm, it closes the flow to the check valves and the carburators are taking over. it is this correct?
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From what I understand ( and someone correct me if I'm wrong), being there's no idle circuit in bottom two carbs, there is little fuel drawn from those two carbs at idle. When the throttle arm hits the accelerator pump , it pumps fuel into those check valves in cyl 3 & 4 and kind of kick starts those two cylinders. That's why the transition isn't that smooth when giving throttle..after about 1800rpms it shoots fuel into those cylinders and she gets moving. Those check valves should stay closed until that accelerator pump gets pushed down by the throttle arm. The pump is what provides enough pressure to open those valves up to let that burst of fuel in.
 
Mattc8821 said:
From what I understand ( and someone correct me if I'm wrong), being there's no idle circuit in bottom two carbs, there is little fuel drawn from those two carbs at idle. When the throttle arm hits the accelerator pump , it pumps fuel into those check valves in cyl 3 & 4 and kind of kick starts those two cylinders. That's why the transition isn't that smooth when giving throttle..after about 1800rpms it shoots fuel into those cylinders and she gets moving. Those check valves should stay closed until that accelerator pump gets pushed down by the throttle arm. The pump is what provides enough pressure to open those valves up to let that burst of fuel in.
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That's the way I though originally, but your post this morning got me thinking in how those two cylinders get lubrication at iddle,and before hitting the 1800 RPM (which by the way the 1800 RPM I guess is related to the adjustment of the cam follower and the throtle cam (page 2C-6 of the service manual)

When you tested the check valves after the issue with the primer bulb, did you have the throttle at iddle for the gas to go out of the check valves when you pressed the primer bulb, or it was at a position where the trigger on top of the acceleration pump was pressed?
Unfortunately the service manual it is not to clear about how the acceleration pump works.
I will do the test pressing the primer bulb with the throtle at iddle (trigger of the acceleration pump out) and at the position of the trottle when it is full depressed and see what the difference is.
Definately those two cylinders must have some sort of lubrication before the carburators kick in.
 
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