Buddy of mine had a 2000 something Johnson do this very same thing. Start up cold then shut it off and fish for 15 to 30 minutes and it was a bear to get started. He took it to Cowtown in Cuba and told them what it was doing. A couple days later and he gets a call from the mechanic and he said there isn’t anything wrong with it. It starts fine. He said you need to reread the ticket!!!! Finally narrowed it down to a stater.