Engine dies at full throttle

[ddesmond4]

I have a 1980 Johnson 70hp. Runs perfect in driveway at all speeds. Idles great in the water. It started acting up at WOT. It ran great at WOT for about 30 minutes then it started to slow down to about idle and die at full throttle. Cleaned and rebuilt carbs, no change. Compression is perfect. Could this be a timing issue? Any ideas? Thanks

 

[fireman57]

Re: Engine dies at full throttle

Welcome to iboats. Sounds like you are dropping spark to a cylinder. When it starts slowing down get some insulated pliers and have someone pull the spark plug wires one at a time and check for spark. Could have coils/powerpack that breaks down under heat or a load. Could also have cruddies in the carbies that ends up clogging a high speed jet.

 

[ddesmond4]

Re: Engine dies at full throttle

Originally posted by fireman57:<br /> Welcome to iboats. Sounds like you are dropping spark to a cylinder. When it starts slowing down get some insulated pliers and have someone pull the spark plug wires one at a time and check for spark. Could have coils/powerpack that breaks down under heat or a load. Could also have cruddies in the carbies that ends up clogging a high speed jet.

 

[ddesmond4]

Re: Engine dies at full throttle

Thank you, I will give that a try, I also plan to check all connections to coil and power pack to ensure something is not loose. Should I make any changes to the timing?

 

[fireman57]

Re: Engine dies at full throttle

No, your timing should not have changed. If you have a cylinder that the spark is suspect in can you swap your coils to the other side or not? I don't have a manual for your engine ( but you should) so I don't know if you can swap them or not. If you can and the problem follows then I would suspect the pack/coil. Cleaning the connections would be my first step.

 

[ddesmond4]

Re: Engine dies at full throttle

I ordered new coils and will install this weekend, I am hoping this fixes the problem.<br />Thanks, I will keep you posted.