I'd go with Bill on the solenoid. One thing you could do is being very careful around the flywheel, disconnect plug wires so she dosnt dry fire hook a good jumper cable to positive side of battery and jump straight to stud on starter. That should eliminate anything between battery and starter. If she spins over good that way, backtrack all the connections back to battery starting with replacing solenoid. Also make sure all your ground connections are good, clean and no corrosion. If all else fails take it by Jones trolling motor in Little Rock. John is a sponsor here and he will help you out. He has all the tools and knows how to do all the checks. He can also rebuild starters.