1998 Johnson 150 Looper Idle Issue

[Jose67]

I have had this outboard motor since October of last year. It runs great and idled great until a couple months ago, it still runs great and has good power but now it has started to have idle issues. I rebuilt the carbs thinking that was the issue but it is still the same thing. It idles good when cold but after I have made a run to wherever I plan to fish and the motor has been off for at least 30 minutes or so and I go to crank it up again it spits and sputters until it dies. I have to fast idle it at 1,200 rpm or so to keep it running until the anchor is pulled up and I can bring down the idle and put it into gear quick and get underway (frustrating) once in gear and underway it runs great. It has been the same thing every fishing for a couple months, idles good when cold and leaving the ramp but once it warms up it will not idle without sputtering. I am at a lost on what to check next, I figure if it was an ignition or electrical issue the problem would be constant no matter if motor was warm or cold. Any ideas on what this might be or what else to check? Compression checked out at 90-95 psi on all 6 cylinders.

 

[flyingscott]

Has the optical sensor been replaced recently? I am assuming this is a carb motor.

 

[Jose67]

I have not replaced it since I have owned it as of October 2016, and it is a carb motor. Rebuilt all 6 carbs and put new float bowls because old ones had stress cracks in them also removed and cleaned carb mounting plates with all new gaskets and o-rings.

 

[flyingscott]

I would take a look at the optical sensor.