My Trailer started life built for a 12ft small Jon boat. I liked it because the springs worked good for my boat. I put on a new 15ft Tongue, added side bunks, and a walk way on the tongue. now its carrying a 15ft Mud Boat, a 23 GDSD, troll motor, 2 batteries, anchor, and side or Loading Bunks. I really hate the small wheels. They sink in the mud and it really takes some Horse Power to pull it out loaded. I was looking at the tires and they are only rated for 720lbs apiece. I was wondering if this trailer is going to hold up to hard use or should I put on a bigger Axle that uses full sized tires. maybe even just get a bigger trailer?

Take a look at these guys.
http://abctrailerparts.com/
Custom axle with hubs for pretty cheap. Depending on dimensions and if it will fit, you can just buy axle w/hubs and new wheel/tire combo and relocate your fenders. My trailer does the same thing. I am running 12" wheels now and they are worthless. I will be adding 15's in the next week or so.

Cost is nuttin, Big tires ROCK. No small donuts for dis guy. Duckdon