1973 18 hp evinrude Driver Coil test

[KC9000]

Ok so weird thing today, took the motor out, started right up, idled great at the dock while I parked the car, took off we were going 18 mph as expected. Then after about 10 minutes WOT I started to hear a miss, slowed down and sure enough we were missing, went to turn it back up WOT would only give me 5 mph . Got home, checked compression 125/128, Checked points and they are good, checked coils and they are good, looked at plugs and one looked fouled, swapped plugs tried to started in bucket and the motor will not start now, checked exciter coil and it gives me a .6 ohm reading that is the same as before this issue so should be good. I tested spark at the plug the caveman way, held the dang thing and pulled the rope, top shocked me and bottom did not. Any ideas on what to look for?

 

[oldboat1]

Did you check or check and replace both ignition coils?

 

[KC9000]

Yeah, brand new coils, new points, new condensers, checked wire continuity. Do you think a condenser for the bottom hole went bad already. I will swap them and see if I get shocked again...lol good ole spark test.i have the old ones. Any way to test condensers?

 

[oldboat1]

I have this among my bookmarks (hear this guy is pretty good): http://www.pochefamily.org/outboard/Condenser testing.html

 

[KC9000]

Here is a video of what's going on, double checked the point gap, tested the condensers, checked spark, and we got good spark. Is the a fuel delivery issue? I did notice that the wire from magneto to top coil is turning green inside the connector, would a bad wire cause this?

 

[racerone]

You have an ignition miss !!!-----

 

[KC9000]

So maybe that exciter coil? Or a bad external coil? I will take them off and test them.

 

[racerone]

The driver coil is common to both cylinders.-----Points must be absolutely clean.----Check al wire connections.------Use timing light to try and pinpoint if upper or lower cylinder has the miss.----You have of course checked the fuel pump diaphragm.

 

[KC9000]

Ok I will check these things, I ha e not checked the diaphragm, think that would cause this? I am gonna put new wires on too, I have spark to both plugs. So maybe I'll start with the diaphragm on the fuel pump.

 

[gm280]

I gave a glance over all the posts and I didn't see anywhere where you rebuild the fuel system. I would start at the fuel pump and filter and CARB! Could be trash in the idle circuit of the carb causing that miss...
If you could isolate the miss to one cylinder, than you could swap ignition parts from one cylinder to the other to see if the miss followed the part swap. If it is missing on both cylinders randomly, look at the fuel system... JMHO!

 

[KC9000]

So I did do a carb rebuild on it early on, but did not check that fuel pump, as this issue just popped up last trip, so on the lake cruising 18 mph I start to hear the miss, so I slowed down and sure enough it was missing, when trying to turn it to WOT it would only go 5 mph. So we fished back to the dock. Like I said, I am definitely getting spark, I held the plugs and they both shocked me multiple times as my wife pulled the cord, just ohm tested the coils and getting same readings on both. I cleaned the points last night with some alcohol and q tip. The fuel pump I will be taking apart to inspect the diaphragm. Hope that's the issue. The only thing I did not replace in the ignition system is the wires from magneto to coils and driver coil. I look at diaphragm, if there is a hole I will replace and retest. Thank you guys big time!!! Im learning a lot.

 

[racerone]

A new diaphragm is about $6.00 or so.----Can't find one then make one.-----The instant nature of the miss would indicate an ignition miss.----The trouble shooting on these motors is so easy.

 

[KC9000]

Ok check Diaphram and we are good there, threw a timing light at it and swapped coils, problem did not follow top coil, it is the top not giving a light and every time it stumbles or does the miss we get a light from the top plug. Bottom light is on of rapidly until the stumble. So this tells me it is further up the line. Wire for that top plug from the magneto has green corrosion inside... I will replace wires and see if that helps. So I am also wondering if the points are bad? I cleaned them with alcohol. Is that enough?

 

[oldboat1]

While you are troubleshooting, disconnect that stop button (risks shorting a coil). It's a ground so tape off the wire ends.

 

[KC9000]

I did disconnect it just in case while troubleshooting, one thing I did notice kind of were was the wires from the points to the coil connector, they are like rubbery, not stiff as I would expect. Not sure if this is indication of bad wires but I'm going to replace them just cause they are inexpensive.

 

[KC9000]

Would the points being a smige off cause a miss like this? I think these points suck, they don't line up perfectly, one is off just a little, when putting the feeler guage in I can feel the back of the connectors touch the guage but not the front, so there not perfectly flush. And that one goes to that top cylinder. Question tho, why did I not have an issue at first? If this is my issue? Not sure yet.

 

[racerone]

Points ( both sets ) must be clean, clean.----Best way to set them is with a meter.-----Point set at the back fires the top cylinder via the other set of points I believe.

 

[KC9000]

I fell I got it all set correctly. I set the points with a feeler guage, but will do it with a meter too. So with the meter, line the flywheel line in the middle of the magneto plate double line, set meter to the beeper, take all connections off the points and touch that and the base, I should get no beep right. Is there any thing I'm missing? I will clean the points too, with nail polish remover? Or what is recommended, I hit them with alcohol already, but I am going to take them off and make sure they are clean

 

[racerone]

Clean points with some 320 emery paper.----Then clean with alcohol.-----Test run.

 

[KC9000]

So got the same issue after cleaning. Would the driver coil intermittently work? I hooked up the timing light again and the light was not pulsing rapidly on both this time. When it does that miss on the top the timing gun emits a light, it seems the bottom is all over the place too. Could that driver coil be going bad? I might just replace it, its like the last part besides the wires them selves.