1974 evinrude 25hp Misfire when idling...

[jaxbchangler]

Hi everyone i have a 1974 evinrude 25hp that has a misfire at idle and when i take off either one of the boots it idles perfect!? I just replaced both coils (because the old ones were cracked and i thought new ones would fix it), the compression is good 125 psi both cylinders, new champion plugs. Anybody have any advice i wanted to go fishing tomorrow.... Thanks

 

[boobie]

That ignition system was a POS. The best I can tell you is make sure the points are adjusted correctly and good and clean.

 

[kbait]

First off, check spark w/plugs out.. spark must jump 1/4" from each plug lead consistently with a blue/snappy arc when pulling the recoil.

If poor/intermittent spark, check condition of the wires coming out from under the armature plate.. especially where they flex. Clean/reset points as boobie^ suggests, and check armature plate for any lateral play when you pull the flywheel. Any lateral play in that plate will translate directly to point gap, and you'll never get it running correctly w/point gap jumping around. Post back if the plate moves laterally, and we'll help w/easy fix. Also, ignition misfires can occasionally cook a condenser, so you may as well change those out while you're in there.

If the spark tests blue/snappy, you may have a different issue. Plugs should be Champion J4C (J6C if used for extended low speed operation), or NGK B6S gapped to .030"

Good luck!

 

[restornator]

idle means on a boat, in the water, in forward gear at your slowest speed. You can't judge performance in a barrel when the motor isn't under load and breathing in its own exhaust.