I pull a 19' Sea Ray bowrider (fiberglass hull and I/O) without problems. My trailer does not have brakes. I also drive like I'm towing a boat.
Last week I did pull around 4,500 lbs (2,500 lbs trailer and 2,000 load) without an issue but I wished I had brakes for that one. I will be finishing up my brake controler before doing that again but it was move it or lose it situation.