I have a 1993 50 hp Evinrude that has been sitting in my garage for 4 years un-used. I decided that nonsense has lasted long enough so I decided to see if I could get it running today. I put the muffs on in the driveway and got a fresh tank of gas. It started ok (although it took a little longer than it should.) but it is idling too high. (1500-1700 or so on average)

After a few minutes of idling, the tach starts to act erratic increasing to as much as 2000-2500 and then it makes a popping noise with exhaust blowing out of the prop and the tach drops down to the 1000-1500 area. The tach starts to increase and every few seconds it sputters and the tach drops again. (I think this may be considered a sneeze or cough)

I started and ran it a bunch of times today (in the driveway) and a couple of times it acted different than what I described above. When I would start it, it would idle at around 1000 and then slowly fall downward and die. The next time I would start it, it would then go back to the high rpm and sneeze/cough routine. Strange.

I checked the plugs and they appear to be ok and don't have that much time on them. The ceramic part is a light/medium brown color and they don't have a bunch of crud on them.

I changed the primer bulb and also tried a 2nd gas tank but still got the same results.

I had the carbs rebuilt about 5-6 years ago at a local chain outdoor store and it was running fine 4 years ago when I last used it. (I ran fogger through it when I put it away the last time.) I didn't have any marine grade carb cleaner on hand or I would have tried that today.

I was planning go fishing next weekend but now I am hesitant because I don't want to do any damage to the engine. (I also hate to pull the boat 75 miles only to find it won't run.) I found another site that said the high rpms and coughs could be caused by running too lean which can cause damage.

I don't really want to take it to a mechanic if I don't have to but my time and mechanical ability are both limited. If you have any ideas or suggestions, please let me know.

Thanks for your help.