I have a 1985 ( im pretty sure) evunrude outboard. I bought the boat used of craigslist and the guy said the motor was rebuilt. I took the boat out and lets just say it doesnt run so great! NOW the symptoms! I'm rollin up river and the boat gets up on plane and im rollin along fine. Then you can hear the motor bog down and the boat goes to a slower idle with the trottle handle still open all the way! I replaced all plugs, they all have a spark. The coils tested good. New power pack. 120 compression on all 3 cylinders. The top and bottom cylinders you can see the blackish on the spark plugs, but the middle spark plus still looks new? Only thing I can think is blocked carb. Any thoughts?