Evinrude Runs great then only with Idle high

I have a 1989 28HP Evinrude on my pontoon. I just took it out of storage this weekend to put in the lake. It fired right up and idled great. The next day I launched it in the lake and again it started great and ran fine. About half way across the lake it started running really rough and stalled out. I could only get it to start with the idle lever in the highest position. Even then it seemed like it was running on 1 cylinder (really rough). I slowly got it home. Today I started it again and the first 30 sec it seemed great. Then it would only run with the idle lever in the highest position again. I first wanted to see if it was bad wires or plugs so I quickly (short cut) pulled one wire off and started it at high idle. It still ran the same. I then did it with the second wire and again it ran only at high idle. With both hooked back up it will only run with the lever all the way up and it is rough.

Typically I jump right to a carb kit but I am new to outboard boat engines so figured someone may have a better idea. Any suggestions?

Thanks

Re: Evinrude Runs great then only with Idle high

well you have spark on both cylinders, that leaves compression and fuel. i would say fuel. time to clean and rebuild the carb. directions in TOP SECRET FILE. here is the kit.
http://www.iboats.com/mall/partfind...=28&gd_search_11578=1989&**********=623278067