Starter spins, but does not engage the drive gear to turn the engine over..

Any ideas what the problem might be?

thanks!

 

I'd have to say that you've been bitten by one of two things, maybe a combination of both:

1. starter shaft splines are gone - major problem due to location of starter at the bottom of the engine where the mud/water sits and eats away at it.

2. Gear reduction Starter drive (bendix) is defective/dirty. Same reason for #1