1975 70 hp evinrude spark ?

[mike godfrey]

I was out with the boat and at full throttle it ran really rough. I checked the plugs and they seemed okay. Checked the spark and the middle cylinder had a weak spark. I changed all three coils figured i would keep the other two as spares. Know the top coils doesn't spark when doing the crank test with a spark tested at about half inch. If I start the engine up it sparks great jumps the gap and a nice blue spark. But it only seems to spark if the engine is running. I also put the old coil back on and it still only sparks when engine is running. The other two spark when i just crank it why is this anyone have this happen to them. thanxs mike godfrey

 

[Joe Reeves]

Re: 1975 70 hp evinrude spark ?

Spark test gap should be 7/16" and spark plugs must not be installed during the test.

Engine must crank over at least 300 rpm in order for the ignition to be energized properly.

 

[mike godfrey]

Re: 1975 70 hp evinrude spark ?

Ok thanxs.I did have all three plugs out when I did the test, maybe the gap was to far will readjust the gap and try it again. thanxs again I appreciate the help.

 

[mike godfrey]

Re: 1975 70 hp evinrude spark ?

Just wanted to say thanxs joe charged the batteries up fully and they all spark great at 7/16 gap now just have to put it in the water and try it out after i add my tell tale water line on it again thanxs alot you guys are great