1984 Mercury 35 hp outboard missing under heavier loads

[rathersail]

Hi everyone, new member, first post. 1984 merc 35 hp starts right up, idles fine. However with just me in the boat it misses just a few times before it comes up on plane. Add one more person and it misses a lot and will not plane.

Clean fuel filter. New plugs. Tried 2 sets of wires, both used but apparently functional.

Thoughts?