The car isn't lighter if it has a 3500lb boat behind it. In order to get 85mpg equivalent, mechanical advantages were waived. Ignoring the fact that you cannot safely tow a decent sized boat with a light framed car anyhow, the power consumption to move and stop a boat on Texas hills and valleys would make the EV overly expensive compared to it's petro compe or. Until they release an SUV with the GVWR close to a sensible tow vehicle (8000lbs vs the 1K for the Tesla) that will continue to be the case. I don't see it ever happening. A diesel-electric hybrid would be sufficient, but the cost would make it undesirable except to be different and make a point. After said point is made, it would be impossible to sell.