No Spark on #2. Sensor Related?

[frustratedboater]

2000 Mercury (Manual) 40hp, 4-stroke, tilt assist, carbureted...
I have no spark on my #2 cylinder and as little of a wiring harness that it is, I've taken it off the motor and ohms checked all wires. I took great care checking the wires on the #2 and all seems well. I don't like throwing parts at motors, but did that with: Stator, Coils, ECM (used), and plugs and the issue followed. I did check continuity at all the smaller plugs around the laynard switch (don't have throttle handle button kill/S.) and continuity checks out.
Will a temp sensor, or heat alarm prevent or hinder ignition that would cause this? It is very odd that considering all these changes the problem still exists and can REALLY use some advice. Been at this motor for months here and there and we're into duck season and my son is getting restless. Any ideas are great ideas!

 

[Paulngl]

2000 Mercury (Manual) 40hp, 4-stroke, tilt assist, carbureted...
I have no spark on my #2 cylinder and as little of a wiring harness that it is, I've taken it off the motor and ohms checked all wires. I took great care checking the wires on the #2 and all seems well. I don't like throwing parts at motors, but did that with: Stator, Coils, ECM (used), and plugs and the issue followed. I did check continuity at all the smaller plugs around the laynard switch (don't have throttle handle button kill/S.) and continuity checks out.
Will a temp sensor, or heat alarm prevent or hinder ignition that would cause this? It is very odd that considering all these changes the problem still exists and can REALLY use some advice. Been at this motor for months here and there and we're into duck season and my son is getting restless. Any ideas are great ideas!

I have the same problem with my 40 HP Mercury (Bigfoot) 4 stroke (carburetor) 3 cylinder motor with less than 100 hours of operation. Several mechanics, after performing their tests, told me the no spark on number 2 cylinder had to be related to the computer. Also # 3 has a weak spark. After having a mechanic install one new computer from Mercury, the problem was not corrected. I then obtained a second new computer from Mercury (per provided Model and Serial Numbers) and the issue still was not resolved (still no spark on # 2 and weak spark on # 3). Swapped coils with # 1 cylinder that had good spark; still no spark at number 2. During this ordeal I had replaced spark plugs twice with new ones and that had no effect. Note that when I swapped the coils, I had also swapped the spark plug that was previously giving good spark on # 1. Then, after being completely frustrated with labor charges etc. , I purchased from Mercury: a new stator, a new pick-up unit for stator, a new thermostat, temperature sensor, a new engine alarm as the original had cracked, complete new engine wiring harness (including the tiller kill switch and on/off switch), a new coil although the other had proved to be working. After installing all these (ensuring that I had proper grounding and connections) I still do not have any spark on # 2 and still have weak spark on # 3. Please also note that I had performed a complete oil change. The only two things that I have not replaced is the low oil sensor and an electric/electronic unit at the top of the carburetors. Maybe I'll get to those someday bat at the present time I am considering using the engine for an underwater mooring block. In other words, I've practically given up on this motor as there may or may not be other extenuating circumstances related to the design/manufacture of my motor; so I have been told that years ago (sometime near my motors manufacture date) a major manufacturer of outboards had sued Mercury for issues related to copyright infringement and won. Whether the information is true or not, I do not know; although I did find on the Internet that a law suit that took place (shortly after the time of my motor being manufactured) and that Mercury had to pay a substantial sum of money to the other manufacturer. If you find out what the problem is with your motor and get it resolved, please let me know. I have been in touch with Mercury Engineers, etc. for several years and gave up on getting it repaired 3 years ago. Now grasping at straws or will use it for a mooring block and then forget all my frustrations.

 

[GA_Boater]

I have the same problem with my 40 HP Mercury (Bigfoot) 4 stroke (carburetor) 3 cylinder motor with less than 100 hours of operation. Several mechanics, after performing their tests, told me the no spark on number 2 cylinder had to be related to the computer. Also # 3 has a weak spark. After having a mechanic install one new computer from Mercury, the problem was not corrected. I then obtained a second new computer from Mercury (per provided Model and Serial Numbers) and the issue still was not resolved (still no spark on # 2 and weak spark on # 3). Swapped coils with # 1 cylinder that had good spark; still no spark at number 2. During this ordeal I had replaced spark plugs twice with new ones and that had no effect. Note that when I swapped the coils, I had also swapped the spark plug that was previously giving good spark on # 1. Then, after being completely frustrated with labor charges etc. , I purchased from Mercury: a new stator, a new pick-up unit for stator, a new thermostat, temperature sensor, a new engine alarm as the original had cracked, complete new engine wiring harness (including the tiller kill switch and on/off switch), a new coil although the other had proved to be working. After installing all these (ensuring that I had proper grounding and connections) I still do not have any spark on # 2 and still have weak spark on # 3. Please also note that I had performed a complete oil change. The only two things that I have not replaced is the low oil sensor and an electric/electronic unit at the top of the carburetors. Maybe I'll get to those someday bat at the present time I am considering using the engine for an underwater mooring block. In other words, I've practically given up on this motor as there may or may not be other extenuating circumstances related to the design/manufacture of my motor; so I have been told that years ago (sometime near my motors manufacture date) a major manufacturer of outboards had sued Mercury for issues related to copyright infringement and won. Whether the information is true or not, I do not know; although I did find on the Internet that a law suit that took place (shortly after the time of my motor being manufactured) and that Mercury had to pay a substantial sum of money to the other manufacturer. If you find out what the problem is with your motor and get it resolved, please let me know. I have been in touch with Mercury Engineers, etc. for several years and gave up on getting it repaired 3 years ago. Now grasping at straws or will use it for a mooring block and then forget all my frustrations.

After 3 years or 6 years, you finally asked us for advice, hijacking a thread to do it. Please start a thread of your own.

 

[frustratedboater]

Soooo, any one can steer me in the right direction (Who knows how to help) I would appreciate it. Thanks

 

[GA_Boater]

I don't see a temp. sensor killing the spark on only one cylinder. I didn't see that compression was checked.

What the serial number - It makes it easier to find info? 3 or 4 cylinder?

 

[frustratedboater]

I don't see a temp. sensor killing the spark on only one cylinder. I didn't see that compression was checked.

What the serial number - It makes it easier to find info? 3 or 4 cylinder?

I appreciate the reply and your time looking at the schematics.. Everything on this motor was rebuild entire lower unit (seals, hub-ring, all..) I rebuilt the powerhead honed cyl.'s,, new rings, valve seals, adjusted, v-lash, etc.. All is mechanically to spec, I did check timing belt notches line up to TDC. I believe it is electrical, but triple checked all, even flywheel magnet strength. I even took a steel 1/4" extension and felt the magnetics in other flywheels (Merc.100hp & 90hp) just to see if they felt similar and they all seemed the be the same.
Another clue, I now have two ECM's and when I switch them out #2 is still not firing on either one. I ohms checked the #2 wires and all show continuity and throughout the harness. My ground is good, it just baffles me.. It's a real shame, I spend $$$ in hops to keep this for a long time running it on my duck boat.

 

[dmwarnke]

I appreciate the reply and your time looking at the schematics.. Everything on this motor was rebuild entire lower unit (seals, hub-ring, all..) I rebuilt the powerhead honed cyl.'s,, new rings, valve seals, adjusted, v-lash, etc.. All is mechanically to spec, I did check timing belt notches line up to TDC. I believe it is electrical, but triple checked all, even flywheel magnet strength. I even took a steel 1/4" extension and felt the magnetics in other flywheels (Merc.100hp & 90hp) just to see if they felt similar and they all seemed the be the same.
Another clue, I now have two ECM's and when I switch them out #2 is still not firing on either one. I ohms checked the #2 wires and all show continuity and throughout the harness. My ground is good, it just baffles me.. It's a real shame, I spend $$$ in hops to keep this for a long time running it on my duck boat.

Did you solve the no spark issue? I'm having the same issue on a 40hp
4 stroke.