1984 70 mercurry out board only running on 2 cylenders

[trhinehart32]

1984 70 mercury out board only running on 2 cylenders . i found that the coil waz bad put new one on and still the same thing so i switch them around to see if it waz the new one but it works what should i try next.

 

[Jeff Lindquist]

Re: 1984 70 mercurry out board only running on 2 cylenders

i have a 1982 mariner 80 horse. just wondering if the layout is close. i found major wiring issues that stopped me from running totally. main white lead wire from stator to switchbox was one. ignition wires to rectifier was another and switchbox to coils i replaced all 8 including grounds. i will try to include a few pic, see if they match up a bit and look for the newer wires in the photos.

 

[trhinehart32]

Re: 1984 70 mercurry out board only running on 2 cylenders

ok i will look

 

[trhinehart32]

Re: 1984 70 mercurry out board only running on 2 cylenders

mine is only a 3 cylinder youre switch box is nothing like mine

 

[PHE]

Re: 1984 70 mercurry out board only running on 2 cylenders

You can check if the switchbox is working by swapping the inputs to the switchbox from the trigger of the one that doesn't fire to one that does and see if the problem moves to the other cylinder. This is with the plugs out, plugged into the plug wires and a wire wrapped around the threads of the plugs connected to ground on the block, cranking, but not trying to start the motor. If the same cylinder is not firing, it is the switchbox, if it moves to the other cylinder, it is the trigger. Remember to put the wires back where they started when you are finished.

 

[trhinehart32]

Re: 1984 70 mercurry out board only running on 2 cylenders

ok ill go try that ...... i have one more ?.....on cylinder 1 beside the spark plug there is a screw whole right beside it .u can see the threds but there is nothing there could that be my problem .and whats it 4.

 

[hotrod53]

Re: 1984 70 mercury out board only running on 2 cylinders

Re: 1984 70 mercury out board only running on 2 cylinders

Work backwards, unplug every plug wire, measure resistance from the plug cap to ground, mine are a about 1000 ohms each. Then measure from the input of the coil to ground, don't remember the value but be sure they are all close to the same. Check the grounds on each coil. Now your into the switch box. Remember, if you have a broken plug wire like I did, it will cause the coil to melt down.

Check to be sure that you don't have a stuck needle valve in a carb like mine did. The motor will run on 1 carb but not well. Remove the float bowls and be sure that they have fuel in them. Ethanol in the fuel will cause the tip of your float needle to swell if you don't run your carbs out of gas every time you are finished for the day... happened to me 3 times already.

Could still be electrical, just be sure.

 

[trhinehart32]

Re: 1984 70 mercury out board only running on 2 cylinders

Re: 1984 70 mercury out board only running on 2 cylinders

ok ill go try that ...... i have one more ?.....on cylinder 1 beside the spark plug there is a screw whole right beside it .u can see the threds but there is nothing there could that be my problem .and whats it 4. i just dont understand what that screw whole wood be 4.

 

[ajgraz]

Re: 1984 70 mercury out board only running on 2 cylinders

Re: 1984 70 mercury out board only running on 2 cylinders

That screw hole is for an optional screw-in temperature transducer.

You have diagnosed "running on only two cylinders." Is this through spark testing?

 

[trhinehart32]

Re: 1984 70 mercury out board only running on 2 cylinders

Re: 1984 70 mercury out board only running on 2 cylinders

i pull the wire off of number 1 plug and the motor dosent chang so i check the fire in it it dosent have no fire . but i just found 2 wires that come from the stator ..a red with a white stripe and a blue with a white strip they are hook 2 a ground and they are hot but cant figer out where they go they where hook on the switch box ground and the motor still runs thats got me puzzled.so my new coil is good but i cant get no fire. them 2 wires i found hook 2 the same ground has 2 have somthing 2 do with it i hope.

 

[trhinehart32]

Re: 1984 70 mercury out board only running on 2 cylinders

Re: 1984 70 mercury out board only running on 2 cylinders

help

 

[trhinehart32]

Re: 1984 70 mercury out board only running on 2 cylinders

Re: 1984 70 mercury out board only running on 2 cylinders

need a switch box where is the cheapes place too get one