I have a boat trailer with surge breaks. The boat is 4000 pounds give or take plus the weight of the trailer. The brakes were not working when I first purchased a set up 2 months ago and I just had the brakes installed. It is a duel axle it has a hole to put a trailer hitch style pin in when backing up so it will disable the system.Guess what I forgot to do? I backed up without even thinking and there was zero resistance I then looked out after parking and saw that I had blown a brake line.The mechanic said that it was not necessarily entirely my fault as the brake line fitting appeared to be defective from the factory.My question is… How much resistance should be on a boat trailer when you are backing up if you forget to put in that pin? As said before there was zero resistance I was backing it up like I had done for the past six months when the system was in active. Would a person be able to feel that the brakes were locking up? Or can I expect if I forget again I will be blowing brake lines and fittings.I am new to Boating with this type of trailer system so there’s a lot to remember and of course this one was a costly mistake. I’m assuming that when you are traveling long-distance is with the trailer you would leave the pin out and as soon as you stop near any marina or ramp immediately put it in even before you decide to back up so you don’t forget.