If your trailer bunks are broken or are in bad shape, it can make loading and unloading your boat difficult; they can also damage the under side of the boat itself if they're bad enough. Fortunately, these can be replaced with relative ease if you use the right materials and take the right steps.
Step 1 - Remove the Boat
Gather your supplies and head out on a day when the area around your lake will be relatively free of traffic. Then, unload the boat into the water and tie it up to the dock. Replacing the trailer bunks will require a couple of hours and you'll want your boat to be sitting someplace safe in the meantime.
Step 2 - Measure and Cut the Boards
Measure the old bunks to determine the size of the new ones. Normally, these are made from 2x4 or 2x6 treated lumber, so take whichever size wood you choose, lay it on a flat surface, and mark your measurements. Cut your bunks at these marks using a circular saw. Then, move the bunk pieces and lay your carpet down on the flat surface next.
Tip: Always wear eye protection when cutting wood.
Step 3 - Cut and Position the Carpet Over the Board
Set one piece of lumber aside for the time being. Both boards will be identical and will need the same amount of carpet covering, so you'll only need to measure it with one piece. Lay the wood flat on the carpet, close to the edge. Adjust it so that you can fold up the edge of the material and cover almost the entire edge. Then, tip your lumber on end away from the edge of the carpet, and roll it over once more on the flat side. Move out about another couple inches from the wood's edge and mark the fabric with a piece of marking chalk; this will make sure that you cut enough material to wrap around the entire board. Also, leave around three to four inches of carpet on the each end, as this will be used later. Move the board to the side, fold the carpet over so you have two identical pieces, and cut.
Lay the two carpet pieces flat again and place the boards on top once more. Adjust the boards so that the ends of the carpet will fall on the edge of the lumber, rather than on the wider, flat side. This position makes it easier to adjust and staple the carpet into its position.
Step 4 - Glue the Carpet
Take the carpet from the board and place it reverse on your flat surface. Now, spray glue on both the board surfaces and underneath the carpet. Slowly rewrap the lumber, and allow the adhesive to dry for one to two hours. Then, staple the carpet to the boards at the matching ends and at the end seams as well. You can trim the overlap now that your carpet is in place, but it can actually help with water drainage in future if left alone.
Step 5 - Mark Fastener Holes
Remove the old bunks from the trailer while the glue is drying and measure the holes where either bolts or lag screws hold them to the trailer. Make sure you know how big your new hardware should be, but also where the fasteners sit in proximity to the ends of the bunk. Write these down for reference, and then transfer them to your new replacement.
Tip: Keep track of the old bunk attachments when you remove them. This helps you while replacing them.
Step 6 - Attach to the Trailer
Drill holes where you've marked with the appropriate bit. Then, using bolts or lag screws, secure your new bunks in place where the old ones were.