Having an issue with my 5.0 305 OMC in my 1988 215 four winns sundowner. When i slowly give it throttle I can get it close to Wot but once I give it full throttle it looses power and speed. If I leave it at 3/4 throttle sometimes itll surge forward with more power then lose power and it keeps going back and forth like that. It has been getting a bit worse and now I can never really get it to wot no matter how slow I give it more throttle. It seems like a carb issue because of the random power surges and how it runs fine until 3/4 throttle. It is worse after running the boat for awhile, doesnt do it as bad when cold. The boat has had the points replaced with a pertonix kit and has had a carb rebuild within the past few years. It hasnt been run for two years but I have burned a full tank through it now and have ran seafoam in it as well. I am suspicious that maybe the secondaries arent opening up like they should but really lost as to where to start to try to get this solves. Thanks in advance.