1984, 115 hp Johnson miss firing

[WaterBeetle]

when idling and when going slow speeds, the engine occassionally pauses with what sounds like a blast of compressed air. It usually continues running afterward, but sometimes it kills the engine.<br /><br />Reading other postings, one possible problem could be that the spark is cut off on all cylinders which could be the stator.<br /><br />What else could be causing this?<br /><br />Thanks

 

[WaterBeetle]

Re: 1984, 115 hp Johnson miss firing

^

 

[WaterBeetle]

Re: 1984, 115 hp Johnson miss firing

Hi fellow boaters:<br /><br />I just read from WetWolf who has a similar engine that his ignition switch was the culprit of no spark. Could the ignition switch cause intermitant loss of spark like I described above? How could I verify this?

 

[WaterBeetle]

Re: 1984, 115 hp Johnson miss firing

Hello Boaters:<br /><br />I tried jumpering the ignition switch, but it still miss fired. I checked for loose connections and I noticed the red plug in the engine was a bit loose (previous owner removed the clamp that holds the connectors together). But the problem is still there.<br /><br />Any suggestions???

 

[Walker]

Re: 1984, 115 hp Johnson miss firing

Sounds like a lean fuel/air mixture at slow speeds and since I don't your carbs have a idle mixture screw it probably needs a good carb cleaning paying particular attention to the idle circuit.

 

[WaterBeetle]

Re: 1984, 115 hp Johnson miss firing

Thank you Walker, I'll give that a try. Will let let you know what I find.

 

[WaterBeetle]

Re: 1984, 115 hp Johnson miss firing

I found the problem, it was rotten gas lines. I ran the engine on a separate gas tank and she ran like a beaut.<br /><br />I'll be replacing the gas lines (it's a built-in tank on a 84 17' Lund Larson,) but first I have a question. When I fill the tank with gas, almost immediately as I start filling, gas gushes out of the vent. Why would it do that?

 

[DJ]

Re: 1984, 115 hp Johnson miss firing

WB,<br /><br />You're building pressure. Look for kinked fill/vent hoses.

 

[WaterBeetle]

Re: 1984, 115 hp Johnson miss firing

I fixed the pressure build problem. The reason for the pressure build was that a part of the gas fill and vent hoses were below the level of the gas tank fittings as the hoses were simply lying on the hull. The previous owner replaced the floor and neglected to clamp the hoses to the underside of the new floor. Therefore, gas sat in the hoses and prevented the tank from venting.<br /><br />Thanks for all your help!