1999,115 Hp Johnson

I have a 1999 115 hp Johnson motor on my 99 four winns, the problem is when it's first started,It runs extremely rough, and misses to beat the band! "Once in a great while" I might hear a muffed (backfire??) and the engine stalls. It starts right up again, but continues to run rough. If I increase thorttle a little, it smooths out, to just a little better. Once I get to the lake, I drop the trim,start to plane, NO PROBLEM, run it at WOT, again NO PROBLEM. After a spin around the lake and pull into the swim hole, it runs fine, when I bring it down to a slow idle/wake, slight missing, but will stay running. After a couple of hours at the swim hole, I start it, starts right up, but again runs really rough, and even sometimes stalls.....are the Johnson motors just warm running motors?? I am the second owner(first was a very old couple that hardly ever drove it), but I've had it 5 years now, and I myself am told by the local marina that the motor only has appox. 160 hours on it(extremely low for a 99) And they were shocked to say the least, because last year I had to put out the money for a new water pump...(wasn't peeing any more,...impellers fins were all bent permanently over,inside the water pump, but it's all good now). If I'm pulling a skier/tuber, and have to shut off in the middle of the lake to change people, starts right up, idles just fine, takes off and runs perfect. Again the rough idle and stalling problem seems to be when the motors cold, or not warmed up yet at a low rpm. Any advice would be helpful. Thank you very much in advance, Draft

Re: 1999,115 Hp Johnson

Draft, What you describe is almost normal. Those motors go into Quicstart mode when they are cold. This raises the idle speed until they are wanm. Now on my '98 V6 it runs rough until warm, it sounds like your idle mixture is a bit off or the carbs are a bit dirty. You might check the color of the plugs after a highspeed run. If they are brown/black, and you can live with it, I would leave it alone. If not, clean up the carbs...

Re: 1999,115 Hp Johnson

Thanks Chris, I will check the plugs, and check out the carbs, and the idle mixture screw. thanks much, Draft.

Re: 1999,115 Hp Johnson

you do not have an idle mixture screw you have fixed jets, and an idle speed stop screw.

Re: 1999,115 Hp Johnson

HI All that responded....I figured out a lot of my problems with starting, and the rough idle....I had a 20 amp fuse, that I found in a small area, "UNDER" the battery holder that was corroded, and so was the fuse port(the place where the fuse goes into), I have no clue from the looks of the fuse, and the port, how I even got it started, and it ran! But all is good now. Thanks for all the help and suggestions. Happy boating to all. If any more questions arise, I will try to pick your brains again. Thanks again, draft