1977 Evinrude 115 Running Problem

"}I have a 1977 Evinrude 115 t

"}I have a 1977 Evinrude 115 that I purchased with my boat. On the first time out, it ran smoothly for the first 45 minutes and then began to sputter. It ran smoothly for a few seconfds or minutes and then would slow down for a little while then speed back up. On the next outing I put carb line cleaner in the tank and the motor ran smoothly for over an hour and a half. On the next two outings I got the same problems that I experienced on my first time out. I am experienceing intermittent performance, where it randomly slows way down for different amounts of time, and the}n will just speed back up and run at normal. I have read lots of forums and the repair manual, but nothing seems to fit the problem exactly. I have checked the plugs, and they are new, I have out more gas conditioner and don''t know what else I should try before I break down and bring it to a dealer. Any suggestions would be much appreciated! Thanks."

"Is this a gradual slowing dow

"Is this a gradual slowing down such as running out of gas, then having the gas supply returned to normal..... or is the decrease and increase of rpms a sudden instant change of power type happening?"

"Sounds like water in the fuel

"Sounds like water in the fuel to me. I would check the condition of the fuel and look for water. If you find it, I would also recommend draining the carbs after you take care of the contaminated fuel problem."