1973 20 hp evinrude ignition problems

[buildcnk]

I have a commercial unit in Canada which shops tell me was the same block and parts as a 25 hp. It has an extra coil under the mag for lights or battery charging etc. It ran great for 5 years with fuel stabilizer, fogging and foot oil changes. Last summer it ran very rough ( I think on 1 Cylinder ) and now it won't run at all. I rebuilt the carb. the spark did not look great so I changed out coils, points, condensers, and plugs. I get 120psi per cylinder. And when cold I get spark alternating nicely between plugs. The problem is now once it warms up it dies and spark is bad again. I have cleaned grounds and checked coils, checked wires for cont. all good. plugs smell like gas when it quits.
In desperation I took off the head thinking maybe head gasket when hot but looks good and changed the impellor and thermostat.
Not sure what else is left... Also cleaned and checked kill switch. it works fine.
Any Suggestions?

 

[fdrgator]

So you replaced almost everything? Does that include the driver coil? Most (but not all) problems with that mag are due to dirty or mis-set breaker points. Are they oil-fouled by any chance?

 

[buildcnk]

So you replaced almost everything? Does that include the driver coil? Most (but not all) problems with that mag are due to dirty or mis-set breaker points. Are they oil-fouled by any chance?

I thought of that so I cleaned them with some brake cleaner and let them dry. The engine started and then ran for 3-4 minutes. I was able to tune the mixture to peak rpm. Then just rich of that. Shortly after that the engine quit and I could not get it going again. I might add that the day before it ran for a while and I thought I had the problem fixed . So put the boat in the water she started up right away and did a couple of 360s near the dock. Then it started running on one cylinder again and finally by the time I got back to the dock it died and would not start again..
And yes toyour question of drivr coil.

 

[buildcnk]

Actually I had taken things apart and noticed 2 coils there so I ordered 2 (not realizing the other one was for charging.) so I have 2 driver coils and get the same results with both.

 

[buildcnk]

points are set to .020 as per research but someone mentioned .018?? but why the good spark to begin with?

 

[buildcnk]

getting good pressure sounds in crank case but could there be some oil and gas coming out the top seal and fowling the points once it heats up?

 

[buildcnk]

getting good pressure sounds in crank case but could there be some oil and gas coming out the top seal and fowling the points once it heats up?

I guess starting over to see if I missed something will be my only recourse. Perhaps the quality of the points/condensers not up to snuff from local dealer.

 

[racerone]

Does the spark jump a 5/16" or more gap on a test device, yes or no ?----Testing is the path forward.

 

[joereeves]

Re-Clean the points with either acetone or lacquer thinner.

Re-Set the points by having the fiber rubbing portion of the points aligned with the flywheel key. Set them so that a .020 gauge will slide thru BUT a .022 will not.

That will get you so close to the factory setting that one couldn't tell the difference.

 

[fdrgator]

Um...wrong motor / year???? The 1973 has the Lo-Tension Magneto, with a "set" mark on the cam. Aligned with key doesn't get it. Tell me if I'm wrong.

 

[joereeves]

Um...wrong motor / year???? The 1973 has the Lo-Tension Magneto, with a "set" mark on the cam. Aligned with key doesn't get it. Tell me if I'm wrong.

buildcnk .... Disregard post/reply #9 pertaining to the flywheel key alignment... Use the "SET" marking on the cam instead.

fdgator...Yeah, I was aware of the ignition setup, glanced at the book to refresh my memory, however I did forget about that "set" mark on the cam. I still have one (#318488) new one left in my remaining stock so I took a good close look at it. Yep... there sits "SET" and it's a considerable distance away from the flywheel key slot. The notice is appreciated.

 

[joereeves]

Um...wrong motor / year???? The 1973 has the Lo-Tension Magneto, with a "set" mark on the cam. Aligned with key doesn't get it. Tell me if I'm wrong.

buildcnk .... Disregard post/reply #9 pertaining to the flywheel key alignment... Use the "SET" marking on the cam instead.

fdgator...Yeah, I was aware of the ignition setup, glanced at the book to refresh my memory, however I did forget about that "set" mark on the cam. I still have one (#318488) new one left in my remaining stock so I took a good close look at it. Yep... there sits "SET" and it's a considerable distance away from the flywheel key slot. The notice is appreciated.


I see that the cam has been unavailable now for a number of years, and back then listed for about $40.00 (YOW!)

 

[fdrgator]

The different cams

 

[buildcnk]

The different cams

Thanks for all of these suggestions and I feel that I have some more trouble shooting to go. Was away on business the last few days but will have a look at the set up tomorrow. Cheers