If the original hinges on your Boler have been replaces with strap hinges or have worn beyond repair the only hinge that will work on you Boler are the hinges available through Scamp trailers. There is no advantage in changing your hinges, they are not an upgrade, usually simply rebuilding the original hinges will make them like new, but if you need or want to install these hinges here are some tips and tricks.
First the mounting holes are different and do not align so new holes need to be drilled, this is not a bad thing because by changing the mounting location you will be able to open the door flat against the belly band, rather than the edge of the door hitting the belly band resulting in door damage. First you want to remove any weatherstripping from around the door or door opening, this will interfere aligning the door. You want the to mount the hinges on the door, take a close look at the hinges, there should be numbers stamped on them, the #1 hinge is the bottom hinge and the #2 hinge is the top hinge. Start by measuring the total height of the door, it should measure about 63″, divide this into thirds which should be 21″ and 42″, this will be where you want to locate the hinges. Position the hinges so the two door side mounting holes are centred on the door flange and equal distance from the edge, drill ¼” holes through the door and mount the hinge by using ¼-20 x 1″ bolts & nuts. (I will provide alternatives for the bolts later in this article).
With the hinges mounted to the door the tricky part starts now. You will need at least one helper but two helpers can be useful. Apply wide masking tape or painters tape to the body to protect it from scratches, hold the door up to the opening making sure the gap on each side of the door is even and the door is as high in the opening as possible but still sits flush with the body, twist the body side hinge leaf so the 2 vertical mounting holes are aligned and an equal distance from the edge of the door opening. (see why you need so many helpers). Drill the top hole in each hinge, install a ¼-20 x 1″ bolt and nut, then drill the lower hole and install the nut and bolt, and finally the third hole. Finally remove the bolts & hinges and remove the masking tape, when installing the hinge back on the trailer use large diameter fender washers on the inside of the body bolts to prevent cracking and flexing in that area.
Reinstall the hinges, but don’t panic if it is not quite perfect, if it is then great, but if not the holes through both the body and the door are normally enlarged to 9/32″ or a common process is to elongate the holes in the direction needed for adjustment with a ¼” drill. An important item to check is if you do enlarge the holes you need to make sure there is equal weight on both hinges. To test, with the door installed and hinges tightened open the door to 90 deg, grab the door edge and lightly wiggle the door in and out, there should not be any easy movement at the hinge ball area, if there is movement at one hinge then the weight of the door is being supported by the other hinge so adjust that hinge so each hinge is supporting the door and the hinges.
With the door hinges installed and adjusted weatherstripping can be reinstalled. it is important to use a soft bulb type weatherstripping, the foam types are too firm and will deform the door or hold the door away from the jam and not allow the door to close completely.
BOLTS: The body side bolts should be installed with the bolts installed from outside, don’t forget to install fender washers on the inside finally use Nylock washers on the inside to prevent them from coming loose. On the door side the thinner the bolt head the better,although rounded head carriage bolts can be used the problem with them is there is nothing to hold the head when you want to remove them. The bolts I prefer to use are called T-Slot Bolts, these have very flat heads but also have flat sides that can be held with a wrench. to improve the appearance from the outside acorn nuts can be used on these two door mount bolts. When using acorn nuts the amount of thread is showing is important, if there is too much thread you may not be able to tighten the nut fully or the bolt can push right through the end of the nut.