What position should this screw be in when engine is running? I ask because we occasionally have revs drop for a few seconds. I am guessing some air getting into system, but canot find where.

Yesterday I fiddled with the screw while the engine speed was dropping. Problem disappeared, but I am far from sure that my action had anything to do with it

Engine normally clears itself when run hard, in gear.

The problem has occurred about twice per year, since engine was new (1100 hrs in 5 years now) and has always resolved itself.

Vacuum gauge was constant during yesterday's problem, at 2" vacuum. We have had it up to about 12" in the past before the engine showed signs of fuel starvation.

We have only the Beta mechanical pump working. Fuel in tank yesterday was 10" below the injection pump. We have had one tank level 20" below with no problem.

Any ideas on how to resolve this rare, intermittent issue before we lose power while docking?