1979 50hp mercury thunderbolt carb issues?

[Extremes31]

I have a 1979 50hp mercury,I've rewired the whole harness and engine wires,I had rotten wires everywhere and 2 coils were not working cleaned and replaced fuel lines ,tank etc..new plugs all are getting spark test with timing light engine starts every time perfect , but it bog to the point of shutting off when more that 1/4 throttle ,how ever If I manually open the carbs (twist little black spring loaded sync thing linking the 2 carbs together) it goes great no stutters or anything I have tried to adjust it with no luck,also not sure all this linkage is anywhere close to set right any thoughts on how to set this stuff ,I thought maybe the carbs were dirty but if it opens up when I manually run it carbs would have to be fine I think it a linkage issue?any ideas or help would be great?