The driver side wheel of my Yacht Club boat trailer wobbles and I can't figure out why. I've jacked it up, pushed and pulled on it, spun it by hand and it seems to be fine but when I'm towing and go around a corner I can get a good look at the wheel through my rearview mirror and it has a definite wobble to it. Anybody have a similar problem and or any ideas what the problem is?

Sounds like a bent rim, while jacked up did it run true? Could also be cracked and only flexing under load. Is it steel or aluminum?

maybe one of the plys in the tire is de-laminating, and is only "wobbling" while under load? I'd switch the tires from side to side, and see if the problem is with the tire/rim, or the spindle/hub.
HRG

Jack up the trailer just enough to get the tire off the ground. Place a can or a brick 1/4" away from the side of the tire, slowly spin the tire and see if it gets closer or farther from the brick as it rotates. The 1/4" gap should remain the same as the wheel spins. To ck for out of round, place the brick 1/4" away from the tread (center of the tire), watch the 1/4" gap as the wheel spins. This is a starting point. To ck the rim you will have to devise something that will keep the same 1/4" gap between the rim and whatever you can come up with. Hope this helps.

Take the tire/wheel to a tire shop where they can spin it slowly on the dynamic wheel balancer. While spinning SLOWLY you should see what the problem may be.
Tom

switch it with the other side ..... see if the problem follows?

I just went through this before heading home from Florida. I could see a definite wobble on the driver's side front tire. I thought it was a bent rim. Once we took the tire off, there was a 10 degree hook on one side of the tire. The belts in the radial tire had shifted. New tire, problem solved.