I have a 2000 70HP 4 stroke that here recently has became hard to start. It used to fire up on the first try now i have to make sure the ball is tight and turn it over like 10 times before it will start up. I thought there was air getting into the system so I changed the primer ball. Once its running it has no problems, runs at 5800rpms and no problem getting on plain. Does anybody have any idea what the problem is?