V-6 to tow?

A buddy asked me the other day if I thought his Dodge Nitro (V-6) could pull a 20-21 foot wake boat to the lake during camping trips. I told him I wasn't too sure if it was a good idea because with my F-150 somtimes my transmission temperature climbs above 210 and I have a 5.4 liter. I also brought up the weight difference and the danger with braking and having the boat overtake him. I brought up the chance of a steep, wet boat ramp and the chance that the smaller vehicle might have a tough time pulling the boat out of the water.

His story is that he has a Dodge diesel that he will use most of the time but occasionally they would go camping and use the truck to tow their camp trailer and the Nitro to tow the boat. The truck would then be used to launch and trailer the boat.

I'm still concerned with the weight ratio but I don't know anything about the V-6 Nitro. Does anyone have any experience with these vehicles? Supposedly they can tow up to 4000 lbs.