2004 V4 Johnson 115; dies and sputters at idle; runs fine over 1,500 RPM

[clj]

Hello,

I have a 2004 Johnson 115, V4, 2 stroke, carb model. I do not use the boat all that often, but up until very recently, it has always run well. Now, the engine starts up fairly easily and idles OK right after it starts. Then, as it warms up, it starts to sneeze and then dies. Once it gets over 1,500 RPM or so, it runs great; pops the boat right up on plane and revs out fully at WOT. Then, when I back it down, put it in neutral to let it idle, it dies.

If I fast idle it in neutral at 1,500 RPM or less, the motor kind of surges; the RPM drops a few hundred or so after it sneezes and it either recovers or dies. If I fast idle it in neutral a little over 1,500 RPM it seems as it if will run like that all day.

I did not remove and clean the carbs, but I did spray some carb cleaner into the carbs and the low speed needle jets and dumped a bottle of Sentry into the tank. Those things made no difference.

I did notice that when it starts to die, if I push the key into choke it, it recovers and runs OK for 30 seconds or so and then starts to sneeze and then dies again. I thought maybe I had some bad gas, so, I hooked up a 12 gallon tank to the motor with known, fresh gas in it and it made no difference. This motor has the Optical Ignition System (OIS) which I assume is fairly reliable and rarely needs adjustment.

Anybody have any suggestions on what I can try before I drag it to the dealer for diagnosis / repair?

Thanks,

 

[guitman32]

Re: 2004 V4 Johnson 115; dies and sputters at idle; runs fine over 1,500 RPM

Try keeping pressure on the primer ball and see if that keeps her running a bit longer. Either way it does sound like a carb issue...

I would also verify head temps at speed to make sure she isnt running lean.

 

[Haffiman]

Re: 2004 V4 Johnson 115; dies and sputters at idle; runs fine over 1,500 RPM

Check the engine temp and see to that it reaches about 145F on both cylinder banks. If less, a defective thermostat most likely.

 

[Solittle]

Re: 2004 V4 Johnson 115; dies and sputters at idle; runs fine over 1,500 RPM

I'm betting on crud in the low speed jets. Spraying carb cleaner usually does not cure this. I don't know the 2004 but cleaning the carbs is a do-it-yourself job if you've a mind for it.

 

[gjmsd]

Re: 2004 V4 Johnson 115; dies and sputters at idle; runs fine over 1,500 RPM

In most carbs I've dealt with, the low speed jets have much smaller holes than high speed jets and are likely to clog first especially if the the engine sits for a while. I had a similar problem and was able to solve it using seafoam. I have a thread going somewhere if you want to search for it. Seafoam will work if the carb jets are not completely plugged, they need at least a little flow for the seafoam to get in and clean. My engine now runs great and idles perfectly.