1975 Evinrude 50hp Jumping Spark

[Jacob645]

Just put two brand new coils on because it wouldn't go fast at WOT. Now it will. The spark is jumping from the boot to the opposite end of the plug. Also it dies when it's brought down from WOT. Usually drops a cylinder first. Here's a video of the spark jumping.
http://www.youtube.com/watch?v=D3nLqZ3uMaI

 

[tashasdaddy]

Re: 1975 Evinrude 50hp Jumping Spark

i think i would change the plug wire. or the plug is bad, because the spark is going to take the route of least resistance. it definately has good spark. get take fixed before taking on the stalling problem. this may cure that.

 

[Jacob645]

Re: 1975 Evinrude 50hp Jumping Spark

I had just bought the plugs in the video. We were thinking that too. The video was actually the first time it had been started with the new plugs, so we ruled that out. What type/size wire should we try to find?

 

[chbailey]

Re: 1975 Evinrude 50hp Jumping Spark

The last time I saw something like that the wire boots were shot or not properly set. I'd go for a set of new wires. Check your lengths and this link should get you what you need: http://www.iboats.com/Evinrude_Prem....268675--list_time.1185926121--view_id.269995

 

[iwombat]

Re: 1975 Evinrude 50hp Jumping Spark

Clean up the facing around the plug hole and torque your plug down properly before trying a new wire.

 

[chbailey]

Re: 1975 Evinrude 50hp Jumping Spark

But if the boots are shot will it matter?

 

[iwombat]

Re: 1975 Evinrude 50hp Jumping Spark

You've got hot spark shooting out the end of the wire, bypassing the plug and going to ground.

That just ain't right.

Y'know the really old spark plug wires had no boot. Just a loop at the end you screwed on to the plug with a nut. The boot just keeps the clip in place - nothing else.

 

[chbailey]

Re: 1975 Evinrude 50hp Jumping Spark

I remember seeing the older model motors with the nut holding on the wire so that jiggled my thinking some. Very good point.

 

[iwombat]

Re: 1975 Evinrude 50hp Jumping Spark

You can even get the plugs to fire if you hold the plug wire near them. Sometimes that will get a fouled plug to get going and warm up enough to fire consistently until you can get to the dock and replace it. Bottom line - get a hot spark near a plug and it's a whole lot easier path to ground than going through the air.

I'd say bad plug, or bad plug ground. Sometimes you just get a bad plug new. It's happened to me before.

 

[Jacob645]

Re: 1975 Evinrude 50hp Jumping Spark

Update: I took the boat to a local dealer (not the one I got the coils from), and they had never seen anything like that. He put a different boot and spring on and it fixed it. I just got back from the lake, and now it runs fine. That apparently fixed the "dying at throttling back" problem too. Also, neither of the cylinders ever cut out the whole time. Thanks for all your help!

 

[iwombat]

Re: 1975 Evinrude 50hp Jumping Spark

That was seriously weird.


Really.