Late 60s Mercury 200, 20 HP twin

[wngnt]

Only one spark plug is firing. I cant see any bad connections. The points visually look OK, both coils have the same resistance. I am suspect of the condenser. Can I test something to figure out what is wrong? How do I troubleshoot my problem? Motor has been running like this for some time. It will drag the second cylinder along, so one cylinder seems to be doing good.

 

[renegadepro]

Re: Late 60s Mercury 200, 20 HP twin

I would go ahead and replace points and as I learned both condensers. Also check all the wiring with an ohmmeter.

 

[aeronutt29]

Re: Late 60s Mercury 200, 20 HP twin

The general rule for isolating a bad part on a dual (or triple, etc) ignition system is to swap one part at a time from one location to the other. When the cylinder that was firing stops firing (and vise versa) you've found the bad part. Considering how cheap a set of points and condenser are, and how old the motor is, you would probably be well off to just replace both sets with new parts. If it still doesn't work right, post again and we'll help you out more...<br />Ron

 

[Chinewalker]

Re: Late 60s Mercury 200, 20 HP twin

Save yourself some hassles - replace the points and condensers - condensers in particular. They're cheap and are the items most likely to give you a headache later on... especially when you're furthest from shore in heaviest traffic.<br />- Scott

 

[EARLS BOAT]

Re: Late 60s Mercury 200, 20 HP twin

If you are a little stapped for cash at the moment, you can take the contacts out and useing fine grit sand paper clean the contacts really good . they tend to glaze over and sometimes still look good. i have had the same problem recntly.