When Gilligan is standing in front of the plane, the propeller changes position twice between shots.
When Wrongway is teaching Gilligan to fly, one of the examples is "what do you do when flying at 30,000 feet". An open cockpit plane and pilot could not fly at that altitude. The temperature would be unbelievably cold and you could not survive without oxygen. BH.
After the engine is repaired and Wrongway Feldman starts the engine, you can see the belt that is turning the propeller. You can see the belt in scenes where the engine is running, but it isn't there in scenes where the engine is not running.
The anonymous hands shown sabotaging the plane's wing strut are clearly Alan Hale Jr.'s.