Intermittant Idle problem

[jons 79 tower of power]

I have a 1979 Mercury 115 HP, 6 cylinder Outboard with electronic ignition. Carbs have been rebuilt, timing set, new plugs, rebuilt fuel pump. water separator filter installed. It ran perfect all last year. This year, the first time out, it had an intermittant idle problem. Idle would be fine most of the time then suddenly, it would surge up and down between 600 and 300 rpm and eventually stall. I would re-start it, and run at high rpm for a while, slow down and it would idle fine for a few minutes then idle rough again. While it was idling rough, I pumped the fuel bulb to make sure it was getting enough gas, with no improvement in idle problem. I am thinking electrical problem? Another time, while it was idling rough, I used the high idle lever to increase the idle speed. Above 1000 rpm it ran smoothe. I would decrease the idle speed with the lever and, when I would drop to 1000 rpm, it would suddenly begin to surge again. Raise it again above 1000 rpm and it sounded good. Help! Any insights out there. Thank you in advanve , Jon

 

[jimmbo]

Old gas? Did you use a fuel stabilizer when you put it away last year? Also when was all the work done to it? Last year, this year?