trouble starting

[Huskie]

When I go to start my 100 HP Johnson, sometimes it will turn over fine (engage the flywheel), but disengage right before it would start or disengage as it first fires but doesn't start. Any ideas? Doesn't do it all of the time, but sometimes this will happen 5-6 times before it starts.

[boatfixer]

Is the battery fully charged and what do the teeth on both pinion gear and flywheel look like? Worn? Sometimes starters that are starting to fail wont rotate fast enough will do just that.