The broken screw turned out not to be the problem with the engine. So now I've changed to 'shotgun' mode to fix the problem. I've replaced all the fuel lines from the tank to the engine. Re-bedded all pipe connections and rebuilt the check valve that keeps the fuel from back-flowing into the tank when a filter is opened. I also replaced both filters and cleaned the filter housings. That was all yesterday and today's engine start went pretty well. The only 'smoking gun' I could find was some gunk in the check valve that was keeping it from working. Could low fuel level in the tank, coupled with the stuck check valve allow air to be sucked into the fuel line from some questionable connection? I sure hope so! I may have to clean the fuel tank to make sure this doesn't happen again.
Tomorrow I'm moving to a different slip, hopefully the engine will start right up and I won't run out of fuel getting from one slip to the other.
John