Idle Problem Johnson 100

[DavidHickey]

Good morning, I have a 1990 Johnson 100 outboard. The engine runs great when warm. It runs rough at idle when cold, but once you take off you don't have a bit of a problem till hitting no wake zones, and after running at a slow no wake speed for 5 or 10 minutes it starts running a little rough. When you go to take back off it bogs until you put it in neutral and rev the rpms for a couple minutes. It almost sounds like its running rich and needs to burn off excess fuel in the cylinders or something. And if I go thru the no wake zones at a higher speed "creating a bit of a wake it seems to eliminate this problem for the most part" I was convinced the problem was the thermostats being stuck open and overcooling the engine at slow speeds. I ordered a thermostat kit and removed the old thermostats yesterday. UNFORTUNATELY they don't appear to be defective. Unless something other than the obvious could be wrong with them. I dropped them in boiling water and they both opened and then closed as the water cooled down. Anyone have ANY ideas on what I might try next? These things just frustrate the hell out of me. FOR ONCE I would like to have a boat that actually runs as it is suppose to! EVEN if just temporarily!!!! EVERY boat I have owned seems to have something wrong with it that no amount of tinkering can cure. But unfortunately I cannot afford a new 30,000.00 boat.
Thanks
David

 

[heflins]

Re: Idle Problem Johnson 100

Link and Sync, but I would Check carbs 1st they prob need rebuilt also if the Recirculation system is not functioning properly you will not Idle correctly it doesn't take much to stop those check valves up and eventually that unburned Fuel/Oil has to go somewhere.
Man I feel your pain I just went through a mess with my outboard and ended up doing the rebuild myself.

 

[dewangy]

Re: Idle Problem Johnson 100

sounds like you have an exhast leak under your engine cover,this makes your motor starve for air at low speeds.

 

[tashasdaddy]

Re: Idle Problem Johnson 100

David you need to get the OEM Johnson manual for your motor.

You should be using Champion spark plugs QL77JC4 gapped at .030 . i would check timing, and do a linc n sinc (manual). i would make sure my carbs are 100%.

timing and carbs are covered here.
http://forums.iboats.com/showthread.php?t=299680