you got it goin in the right direction. I think you'll have plenty enough power with what you got. coils are easier to change than the whole engine. My backhoe ran off a 14hp 321 Kohler just fine I only up graded to 18 because it was FREE and a lot quieter.

I know a lot about a lot of things BUT I still have a lot to learn.
Life is what you make of it. So, why not make a working machine to make it easier.