Here is an update:
I have now gone on many longer trips pulling my pontoon boat along with camping gear and a dog.
Estimate the gross boat and trailer wait at 4300 loaded, another 700 of people, gear and dog in the car.
Honestly it pulls quite well. It is very happy at 65mph in 4th gear getting 10mpg.
I have and HIGHLY recommend you get rear airbags installed for safety and stability. Well worth $200. I put mine to about 25psi.
I also have a transmission cooler installed and monitor my transmission temperatures with an OBD2 adapter. Trans temps stay at a consistent 170 F and that is in 90 degree heat.
Mainly in Wisconsin which is hilly in many parts but no mountains. Trans will spike maybe twice a trip to the 190s on the very long inclines for less than 1 minute.
Unless you live in the mountains I do not see any reason you would have trouble pulling a large pontoon and heavy double axle trailer. Mine has surge breaks and everything stops very quick for so much weight. I would not pull without trailer breaks (have tried it on the 4runner and took way to long to slow things down).
Just drive safe at 65, give yourself room, stay alert and you are all set!
The pic below is before I put the airbags in. With the bags it sits at the same height as when not loaded.
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