I am replacing some old worn seats in my boat. I am also replacing the rotten wood that is used on it as well. What kind of wood is best to use? I don't need a lot, just 3 strips about an 1 1/2 inch thick and 8 inches long.

I just made a template out of some old wood I had laying around. I got some blue spray paint and thought I would just do that. Not wanting to spend alot of time and money on it.

Any ideas as to what I need to do ? Should I do something different? Here is the seat I am replacing, with the wood below it as support over the compartment.
Should I treat the wood with anything or should I just spray paint it and just be done with it.