1972 20 HP ignition nightmare

I know you guys have addressed the issue with this ignition system before and I read most of the post. I was looking for a step by step way to check each component of the ignition system. Is there such a thing? What kind of tester checks the condenser these days? I do not understand how to get from point a to point e? Please go easy on me, this is my first merc and after this I might go back to the C horse. Just my luck that I picked this one right out of the gate.

First thing I found all of the wires disintegrated so I thought I would just replace them. I took the top orange cover off the ignition plate and no problem just unscrew the wires and replace them. Penk, screw broke right off flush with the plastic. Ordered another one and think I got the last one in the country (OEM) And what ever happened to an assembly being all of the components included? I just got one piece for a mere $150. A bit pricy? Then the wires going to the little white insulator blocks were also disintegrated so I ordered those as well but they sent both in brown. I didn't get a white wire but what do I care as long as it will work and I know which wire it is. Found the last of those as well. So before I put it all back together wanted to check the coils and condenser. I had a digital meter but somehow the values were off. It appeared that the high speed coil is bad but I want to make sure I am reading it right. I had to give back the borrowed digital meter and now only have an analog meter. Can I still check coils with my analog meter? Any help would be appreciated. I really don't want to throw more money at it but I have come so far.

Re: 1972 20 HP ignition nightmare

If you are just checking DCR then the analog will work; that's all we used to have. However the digital gives more accurate readings. The DCR check really doesn't check the coil as you could have a shorted turn or two and it not show up. Additionally, if you have a high voltage problem, it won't show up till you power it up. Biggest thing on the coil to me would be external corrosion that occurred during long periods of storage; like the wire from the inside the coil to the external connection corroding to the point of being electrically unusable. Other points would be external tracking between the hv connection and the dc connections. In some cases the bakelite case breaks down and an arc can occur from inside the hv cup and go straight through the insulation to a dc terminal. A good fitting cap on the hv lead helps along with some silicon grease to help prevent the presence of air. Air contains oxygen and high voltage can excite the oxygen molecules in air and create what is known as Ozone (O subset 3). It is highly corrosive and can cause electrical breakdowns over time.

Mark

Re: 1972 20 HP ignition nightmare

Another common failure point in the old points ignitions is those white plastic insulators, they have a habit of cracking or burning an arc trail when the voltage arcs to ground.

They are now NLA but CDI Ignitions have found a source and have save many owners from scrapping an otherwise fine motor.

Inspect those insulators very carefully in good light, an arc trail can be very faint. These will allow spark during a spark test yet totally fail once under compression, making you pull out hair, curse the sea gods, turn grey at an early age, and wonder what you've done wrong.

Don't ask me how I know.

Re: 1972 20 HP ignition nightmare

Hi Flipper here are some links that may be of use to you.


1972 Johnson 20R72R 20 hp Outboard Motor Parts

3 HP Evinrude Lightwin Ignition System Tune-Up 1952-1967

Maintaining Johnson E & FD Serie