Re: Odd tire wear
To answer your question, you can measure your tires outside edges from side to side at the top & bottom to determine camber. If the values are equal you are good. If the bottoms are farther apart you have negative camber. Your description sounds as if you have negative camber on the left side only. To isolate that you can put the trailer on a perfectly flat spot and check with a capenters level held vertically against the outside of the tire. If the bubble is more to the to the outside on the left side there's your negative camber. It won't be perfectly level due to the bulge at the bottom of the loaded tire. I can tell you that in cars & light trucks with straight axles (rear) there is usually zero camber. The aligner we use where I work can report variations as small as .01 degree. In articulating suspensions like front ends and multilink rears, camber values can vary by .5 degrees and be acceptable as a rule of thumb.
You can measure the front & rear of the tires to determine toe value. This should also be zero.
I assume you have a straight axle as most boat trailers do. You don't have a crank axle by any chance, where the axle tube is stationary and there is a crank pivot at each end? The same descriptions would apply, but they would be harder to measure if the trailer or boat blocked your measurement.
I think you would need to get the boat off there to measure across the tire tops on most of the boat trailers I have seen. The problem there is that without the weight of the boat you could get wrong readings. If there's no bearing problem I'd recommend the level check and then the measurement. It could tell you quite a bit.
As far as loose bearing, that's easier, and it's more likely the problem. Put your foot on the top outside of the both sides tires and shove em hard. Try to rock the trailer sideways against the bearings and tires. If you feel a clicking that's suspicious. Then chock the right side, pick up the left side and try to rock the wheel from side to side + top to bottom with your hands, also spin the wheel. There should be no play in the bearing and it should spin smoothly on it's axle. No sandy crunchy sounds. If the left side feels smooth check the right side too. I hope you have a bearing issue, it's cheaper and easier to fix. If you need to know how to change the bearing there are lots of video's and info here, or on RV.net or youtube.
