75hp 2-stroke Bogs Mid-Throttle Only

[guitarplaya39]

1994 Merc 75hp 2-stroke started bogging while cruising. Noticed the primer bulb was empty (not sucked in) when this happened. Replaced both filters, fuel lines, new primer bulb, and removed anti-siphon valve.

Now she only seems to bog down at mid-throttle. Not completely, but you can hear and feel the power surging. Runs fine for extended times at idle/low speed and high/WOT. No problems getting on plane if I make sure it's primed before taking off.
Is this a sign of an air leak somewhere? Could the fuel pump be failing? Or could this be something more invasive like carb or compression issues?

 

[Faztbullet]

Replace the fuel pump diaphram and pull a carb bowl drain screw. Let the fuel filter thru a white paper towel. If it leave black specks fuel lines in engine need replaced as they degrade from the inside

 

[guitarplaya39]

Replace the fuel pump diaphram and pull a carb bowl drain screw. Let the fuel filter thru a white paper towel. If it leave black specks fuel lines in engine need replaced as they degrade from the inside

Alright I'll give that a try. I did a visual inspection of a couple of the lines when I replaced the inline fuel filter and they appeared okay inside, but I'll check the carb drain.

 

[guitarplaya39]

What kind of carb issues would cause it to only surge at mid-throttle?