I crawled under my boat today and peeled some of the carpet back on my bunk boards. I was curious as to when I should be replacing them. Well, needless to say they need replaced in a bad way. The wood has turned black and is very brittle to the point you can stick your finger through in some places.   I honestly don't know what's holding the boat up off the trailer. You guys using treated lumber for replacement or what? I even thought about some of that new plastic lumber, wouldn't have to worry about rotting then. What do you think? :-/

It all depends on what type of boat you have as to what type material.  The man made stuff if not carpeted would have the potential of being slick and maybe causing some problems.

I only use treated lumber when I have to replace a bunk.  I get the measurements and prepare a new one, put it in the truck and head for the lake.  I let someone fish with my boat while I am changing the bunk.  It usually only takes a few minutes.

I noticed the carpet on your bunks looked a little bad when we took out that morning.

You might have something there with that plastic lumber.  Cover it with a good marine carpet and it should outlast the carpet.

Just for the heads up...

There are different grades of pressure treated lumber.

    Above ground

    Below ground

    In the water

I have no clue which you have, but this may be something to look into.

After you rebuild, Thompsons Water seal is one of the best things you can do. My dad uses it on the floor of the horse trailer, and the boards are good as new 20 years old.

Try this

http://www.bunkaps.com/index.html

Or this

http://www.ultimatebunkboards.com/

You might have something there with that plastic lumber. Cover it with a good marine carpet and it should outlast the carpet.

X2!!! 8-)