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The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
In addition to anything else, I'd be concerned about the transmission overheating on those grades and would install an aftermarket fin tube cooler. I'd probably beef up the suspension on the Montero, too. Of course, having the boat as empty as possible would help.
I tow with an F150 and glad I do since I tow on longer distances and through the Canadian rocky mountains!. However for such a short trip I would just slow down and be very smooth on the accelerator so the transmission doesn't work too hard. Highway driving at 45 MPH should be considered. An aftermarket transmission cooler would be good though. Since your boat is a 2008, I'm expecting the trailer breaks to be good if not excellent. Randy Kolb (Nautiduck) tows with an SUV similar to your I believe. What he did is to beef up the trailer breaks by chaning them to disc breaks. I believe he also added a transmission cooler.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.