I Noticed that I busted two brackets off of my trailer bunks.  I was going to replace the brackets but figured it may be time to replace the bunks on both as well.  My question is what type of wood is usually used?  Marine grade or just treated?  I saw that BPS has pre carpeted bunks available but they are too small for my needs.  Any links or advise would be great.  Thanks in advance

I used the non-arsenic Treated Wood.  Replaced my 4 years ago, no problems yet.  I have not see Marine Grade wood in years and that was 5x10 plywood without voids.

Is there even a type of synthetic bunk on the market?   :-?

I looked at the synthetic Deck stuff at Lowe's.  I was not sure if the synthetic Deck stuff  might be more likely break that wood.  I went with 2x6 wood.

I put synthetic wood on my bunks on my old Tracker about 8 years ago.  It is heavier but will never rot or break.  A little more expensive but I think it is well worth it.

I put synthetic wood on my bunks on my old Tracker about 8 years ago. It is heavier but will never rot or break. A little more expensive but I think it is well worth it.

Do they flex similar to wood when loading the boat on the trailer?  My old and new wood one flex a lot.  Did you carpet the synthetic wood ?

Probably flex a little more than wood.  I didn't use the decking.  Just got some 2 x 4's.  Cuts, glues and staples just like wood.  Just be sure to countersink your bolts because you can't pull them into the board like you can wood.  I put carpet on it.  Just Home Depot indoor / outdoor, but should have gotten a little better quality, as it is starting to wear through.  

Use these and you will never worry about bunks again.

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

I used the non-arsenic Treated Wood. Replaced my 4 years ago, no problems yet. I have not see Marine Grade wood in years and that was 5x10 plywood without voids.

Same here no issues