This weekend I had to relocate my 23' boat from NY to MA and while on the LI ferry after loading truck & boat on the ferry exactly where I was asked to put it (total rig is over 50' from the front of the truck to boat prop) , I was asked If I could move it over one lane. After making an ugly face at the guy, I had to back up the rig up the steep entry ramp. I have trailered before and it was not a big deal to do it but I could feel that the surge brake engage...The weight of the boat/motor/fuel.. going in reverse up hill is enough compress the master cylinder. I did not have to go very far but it was the first time it ever happend to me. (I don't trailer very often) I suppose if you had do to it, you could wedge a 2X4 in the hitch so that the cyclinder would not compress.

Most trailers with surge brakes are supposed to have a reverse lever on the hitch next to the master cylinder. I know mine does so when you want to back up, throw the lever to reverse and the master cylinder throw rod is locked out preventing the brakes from engaging. Most times when baking slowly on a level surface, I don't need to lock them out, but the inertia, when rapidly backing or up a hill as was the case with yours, is enough to actuate the brakes. take a look at the tongue of the trailer and see if there is a lever there for that purpose.

will do thanks....

Or look for a lock out solonoid on that surge unit. mine has a wire that goes to the reverse light on the truck.You're lucky, mine won't budge in reverse when the brake engages.Another trick on a lot of trailers is to stick the s hook of the safety chain into the throw of the actuator so it can't engage.
Bill

Sman there may be a small hole in the coupler that a pin is to be put in for reverse. It took me a while to fig. out what it was for.