85 Mercury outboard with Thunderbolt ignition. Won't idle. 1970's

[Chevrolet2]

Need some help please,
I checked the compression on the motor and it is as follows: cylinder 1)80, 2)90, 3)100, 4)80.
I can start it and it will run but with kick back(like back fire). The interesting thing is that if I disconnect #2 spark plug, the engine will idle great????? I don't understand why? You can hear the miss though.
I checked the spark on all the plugs and it great (lots of spark).
The fuel ball can be pumped rock hard before the engine starts, but after it idles, the ball goes soft.
I took the cover off the carbs and could see lots of fuel.

Any ideas or suggestions.

 

[merc850]

Re: 85 Mercury outboard with Thunderbolt ignition. Won't idle. 1970's

If that is a distributor type ignition take the cap off and check the cap for carbon tracking between contacts and from center carbon to contacts. The rotor is formed on the shaft so don't try to remove it but check it for corrosion. You can also run motor in the dark to see if any of the plug wires are cross-firing.

 

[Chris1956]

Re: 85 Mercury outboard with Thunderbolt ignition. Won't idle. 1970's

Check to make sure the wires are on the correct spark plugs. The dist cap should have cast in numbers. Obviously the top cylinder is #1, and the bottom #4.

 

[Chevrolet2]

Re: 85 Mercury outboard with Thunderbolt ignition. Won't idle. 1970's

The wires are in the correct location. What is bothering me the most is that it runs so good with plug wire #2 disconnected. It does not have points, It has a stator and trigger. Is the compression values OK? Some repair manuals say OK but I really don't know.

Thank you for your reply.

 

[turtles11756]

Re: 85 Mercury outboard with Thunderbolt ignition. Won't idle. 1970's

the primer bulb should stay hard if the tank is full ? check fuel pump, gas lines. see how it runs if you choke it some. the compression should be closer to 130lbs. psi and within 15% of each other cylinder. try another guage