40 HP 2 stroke engine problem

[harnish boat03]

While coming on the fast acceleration going to full throttle the engine will intermittently bog down and sputter, never reching full RPM of 5000. Usually 300-600 RPM lower, once it totally cut out. Both carbs are getting fuel (whether restricted or not) and the spark looks clean at the plugs. The fuel filter bowl looks normal. Any thoughts?

[boats.net]

May need to remove and clean carbs.