advice on 40 hp not firing on two cylinders

[swartzjay]

I have a 1991 Mercury Classic 40 hp and am trying to get it the start. Checked compression on all cylinders and they are all around 120 except #3 is at about 90. Cylinders #3 and #4 are getting new spark. Moved around coil pack #1(good pack) to # 3 and 4 and no spark still, so i know thats its not the coil pack or wires. So i was thinking about moving red/red white to Blue/blue white to test it that way. Would that be a good idea to maybe test for stator issues and switch box issues? Any advice would be appreciated. I was also wondering how to time this engine as well. Thanks

 

[sxmerc]

Re: advice on 40 hp not firing on two cylinders

I think you need a switchbox if you're missing fire to 3 and 4.

 

[1nebel0]

Re: advice on 40 hp not firing on two cylinders

Don't be so quick to condemn the switch box....Could be the trigger!

 

[Mi duckdown]

Re: advice on 40 hp not firing on two cylinders

cylinder # 3 is 90.??

 

[12vMan]

Re: advice on 40 hp not firing on two cylinders

Don't be so quick to condemn the switch box....Could be the trigger!

True..I would check that first

 

[swartzjay]

Re: advice on 40 hp not firing on two cylinders

first of all I appreciate all of the help yall. I switched the wires around like i said i would and still no fire on #1 and #2 cylinders. Does anyone know if the switch box or trigger needs to be replaced? Or any way to maybe check to see if the trigger is bad? Any advice on that issue would be helpful.

 

[Sunfish12]

Re: advice on 40 hp not firing on two cylinders

When you switched the wires did you use the known good switch box?

 

[swartzjay]

Re: advice on 40 hp not firing on two cylinders

I meant cyl #3 and 4 . And i think the swithbox is bad and am going to just replace it. thanks to all