misses very badly when warmed up?

[mickuk]

I have a 1989 evinrude 20hp, when it gets warm after about five mins it will idle perfect but misses badly when revved.<br />I have stripped carb three times, but then realised that it ran perfect when cooled down again.<br />Could it be the coils/cdi units(the two black units that run the spark plugs?)<br />Can they run ok when cold and badly when warm ?

 

[fireman57]

Re: misses very badly when warmed up?

Could be the coils. Check for spark when it does this. Should be strong blue. If you have a buddy give him some insulated pliers so he can pull the plug wires one at a time when it is doing this. If the rpms don't change when he pulls a plug then swap the coils. If the problem follows then I would suspect that coil. You might try cleaning the grounds to them first, especially if you are around salt water.

 

[mickuk]

Re: misses very badly when warmed up?

Thanks for reply<br />just tryed pulling plug wires off while running and got good spark on both coils, but when it starts missing badly, it misses spark on both coils?<br />Could my problem be further back, what is the next component back to check?<br />all ideas appreciated.

 

[fireman57]

Re: misses very badly when warmed up?

If it was missing spark on both coils it will not run. Are you checking spark after it is warmed up and starts missing?

 

[mickuk]

Re: misses very badly when warmed up?

yes checking spark when warmed up, when it misses it jerks the engine and spark looks like it misses at the same time every couple of seconds.<br />this is all at about half throttle, at idle i cant notice any differance,it seems fine?

 

[fireman57]

Re: misses very badly when warmed up?

Still sounds like a bad coil. Can you determine which plug is not sparking? IF you can then swap the coils and see if the problem follows.

 

[mickuk]

Re: misses very badly when warmed up?

will have another try and post back tomorrow as my boat is in harbour and tide is out now.<br />thanks for the replys fireman57

 

[fireman57]

Re: misses very badly when warmed up?

You might check your flywheel key. It could be sheared or sloppy and will cause a timing problem. If that is it make sure when you change it that you torque it to the right pounds. I don't know what they are as I also don't have a manual for your engine.

 

[mickuk]

Re: misses very badly when warmed up?

This problem seems to be leading to whatever lies under the flywheel? some kind of coil/coils.<br />does anyone know what lies under there on this model and if i can get bits please.<br />not getting much help over here.<br />thank you

 

[mickuk]

Re: misses very badly when warmed up?

just found out thermostat is full of salt causing overheating don't know if cdi is permenantly damaged yet. should have flushed it out will i ever learn.

 

[fireman57]

Re: misses very badly when warmed up?

Salt water will do that to you.