If you use 'pin'. You have to pin it in an action. A specific instance to another specific instance.
With 1 boat you just do it in the 'on start of layout.
But i suppose you will have more boats. Then you have to do it on creation. Preferable combined with the use of containers.
Create the boat. (when using a container it will auto create the turret)
Place the turret (it will be automaticaly in a picked state, so no additional picking needed)
Pin the turret to the boat. (due the container the right boat and the right turret wil be picked)