70 horse Johnson stalling, spark plug question

[marcusknight]

I have a 1979 Johnson 70 horse. When I bought it I replaced the spark plugs with Auto Lite 2634 plugs. They worked quite well. I recently replaced them again with Champion Plugs this time. QL77JC4 which is supposed to suppress RF interference. There is also some dispute as to what gap to put the spark plugs at. Either at .030 or .040. I recall I set them to 030 this time. However, I am noticing more times now than before that the engine is stalling. For example, it will quit when I put the engine back to neutral after running it of a while. It will not die right away, maybe after 30 seconds in neutral. It will also do this when I put it in slow forward, the slowest it can go. I think this problem has something to do with the change in spark plugs. My question is, do you think it has something to do with using the resistor plugs or that the gap may be set different this time?

 

[TwoRivers]

I have a 1979 Johnson 70 horse. When I bought it I replaced the spark plugs with Auto Lite 2634 plugs. They worked quite well. I recently replaced them again with Champion Plugs this time. QL77JC4 which is supposed to suppress RF interference. There is also some dispute as to what gap to put the spark plugs at. Either at .030 or .040. I recall I set them to 030 this time. However, I am noticing more times now than before that the engine is stalling. For example, it will quit when I put the engine back to neutral after running it of a while. It will not die right away, maybe after 30 seconds in neutral. It will also do this when I put it in slow forward, the slowest it can go. I think this problem has something to do with the change in spark plugs. My question is, do you think it has something to do with using the resistor plugs or that the gap may be set different this time?

What caused you to replace the Auto Lites?

 

[marcusknight]

They had been in there for many years and it was due to be replaced. So I replaced them with Champion which is the preferred brand according to the manual.

 

[TwoRivers]

They had been in there for many years and it was due to be replaced. So I replaced them with Champion which is the preferred brand according to the manual.

Put the auto lites back in and see how it runs.

 

[marcusknight]

So I replaced the resistor spark plugs ql77jc4 with the non resistor champion plugs. Same model number, just drop the Q at the beginning. It runs now idling without stalling out it seems. I was considering adjusting the idle screw but I thought it was interesting that the engine is running at idle at about 1100 RPMs according to the tach. I also thought it was interesting that the screw currently does not even contact the the actuator that controls the speed.

Watch this video and see if you have any observations. Also does it sound like its idling too fast? It doesn't sound that way to me but see what you think.

http://youtu.be/2qEB0hG2buI

 

[marcusknight]

No Title

Specs are:


1979 StarCraft SS 16ft Blue
Johnson 70 HP 1979 Sea Turtle