I have 1999 115 Johnson outboard on my pontoon. I've owned it for a year. It has run fine this summer, except this past weekend I had a starter issue. When I went to start it, the starter spun but didn't engage the motor and turn it over. I tried a few times over ~10 minutes, and eventually it finally engaged and started right up. I had the same problem the next day. I checked the battery, and it is fully charged. Later in the afternoon, it didn't have this problem. Is this likely a bad starter, or is there a switch that could be going bad?