Rough Idle

[geo7]

Mercruiser 120 1983 153 cid. I found the noise in the timing cover and fixed it. While I was working on it I installed the Pertronix module. It sure improved starting. I installed new wires and plugs. Set timing 8 BTDC. Carb was rebuilt. Now the problem. Motor starts and runs but is not smooth. Plugs seem to have black carbon on them. Do the wires from the distributor need to be crossed? I have run them straight to the plugs. Carb adjustment is 1 1/2 out. It will change the idle if I turn it in, but it still runs rough. What am I missing? Thanks in advance.

 

[thumpar]

Re: Rough Idle

Did you run a full 12v to the pertronix unit?

 

[Don S]

Re: Rough Idle

Do the wires from the distributor need to be crossed?

Not sure what you mean by that, but the do have to be in the correct firing order 1/3/4/2.

That 1 1/2 turns out is only a starting point, you have to adjust them for best running on a warm engine.

 

[geo7]

Re: Rough Idle

I ran a jumper from the Battery and it did not change anything. The Pertronix is getting a full 12v at the coil. Don, the 1 1/2 turns out with motor warm. If I turn it out more it does not change anything. If I turn it in it will lower the idle to a stall. I have the firing order correct but heard that it could jump spark if the wires are not crossed. Do not know where this came from. I am at a loss to smooth out this engine. Thanks for the reply.