Intermittent problem at full throttle

[Putte]

Hi, I have a 1989 Evinrude outboard 40 HP and I have experienced an intermittent problem lately. After a couple of minutes problem free driving, starting with cold engine, at 75 to 100% throttle it, most of the times, starts to coff"" and I have then to go down to some 15 to 20% and no coffing. The beeper does not sound. Same scenario almost every time. Haven't done any trouble shooting yet, don´t even know where to start. Anyone who have any thoughts?
Thank you!

 

[fireman57]

Re: Intermittent problem at full throttle

When it does this check for spark as you may be dropping a cylinder due to a bad coil. Also check the head with your fingers for overheating. you should be able to hold your fingers on the flat part of the head for six or eight seconds before it gets uncomfortable.

 

[Putte]

Re: Intermittent problem at full throttle

The head felt just lukewarm so I believe it is not a overheating problem. It tends to be something with the ignition circuits then..

 

[fireman57]

Re: Intermittent problem at full throttle

Take a buddy and a timing light next time you go. When it acts up check for spark on each plug.

 

[Putte]

Re: Intermittent problem at full throttle

Good advice! I will make some tests during the week-end to come.
I did also find an interesting thread from 2004, initiated by Beck, regarding the SLOW function that gave some hints about possible causes.

Thanks for a very useful forum!
Putte