I agree with what everyone said however, another issue for tire wear is when your trailer has sit for 6 months without moving (during the winter months), leaving in time, a flat spot. It may not happen the first couple of years however, in time, the weight of that boat will put a lot of pressure on those tires esp in the winter when the tire pressure will drop a couple of lbs. As far as marathons go, Great tires. I replaced mine the winter before last. The tires I had on there were 11 tears old. Never a prob with them. Tires will start breaking down at around 7 years. Sure, they will last as long as mine did if you take care of them i.e, proper tire presuure, check for wear, etc, but after 7 years, your on borrowed time..
Max