How often do banks go after a defalted boat loan?

I owe 10k. Do they usually mess with this amount or take no action?

I'd say... 100% of the time. A boat loan is a secured loan. You don't hold title free and clear and never will as long as the obligation is outstanding. They WILL take the boat, and /or sue you for any balance. Pay up or deliver the boat to them or expect to be in court.

And when I said go after a defaulted loan, I plan to return it back to them, I meant how often do they actually sue for the remaining balance.