bogging issues at full throttle

[cowboy]

Good morning , i recently bought a 1977 johnson 55 hp engine that idles fine and is alright at low speed , but once i open it up it bogs down . Now the first time out it opened up fine but when i slowed it down and went back to full throttle is when it started bogging and never righted itself again . I put new plugs in but to no avail . Any advice will be greatly appreciated , thanks , Jeff

[boats.net]

Check mechanical linkage and see if spark advance and carbs are opening completely. Check fuel system for trash and or water in it.