2001 trailer fuse protection

[hutch]

Was coming home on hwy 91, towing 5th wheel and boat behind it. I started to slow down, gave it more pedal and no luck, looked at boost gauge and it was on 30. Then turn turn signal on to pull over and it didn't work. Got stopped and jumped out and pulled the 5th wheel plug from truck. The flashers would work then, so I started to pull out to limp home 20 miles but my 5th wheel brakes was still on. I then disconnected the 5th wheel batterys and that released the brakes. Got home OK. parked and then open the front compartment and boy did it smell of smoke. Went in the 5th wheel and looked under the bed and it had burned the carpet and a coat. The main wires coming in from the truck was melted. The wires running to the boat in back was also burned. Why didn't a fuse blow? I started to check out why and was told by the dodge dealer the fuse for the trailer tow package on 2001 thucks is 40 amp. It runs the brakes, running lights, battery hot wire and all others going to trailer. Some of the wires are only size 16. Was a wake up call for me. Going to put in my own fuses. Getting bid on damage thursday. The short was on the boat trailer. Lucky I didn't lose it all.