How is the 5.9 more capable than a 4.7? You're right.. Need to control the weight but again, how does the motor differ? The 4.7 is fairly close in terms of power output..

His durango does have low range...as all 4x4 durangos do. As well as AWD trims.

Doubt he will need a shift kit as this is local hauling. Just turn off the OD via switch control.

 

The 5.9 has way more low end torque, like the max of a 4.7l at only 1500rpm. The bigger the motor the easier it tows, why do you think the 5.9l is rated at 7300lbs and the 4.7l at 5700lbs (look at the old saying in my sig)? The shift kit is to increase drivability and durability. The transmissions behind the 5.x motors really benefit from from shift kits. The new transmissions behind the 4.7 and 5.7 just learn around them and don't do anything. As for the 4lo, we had one member who had a thread wanting to replace his transfer case that only had awd and 4lock, no low range. They are rare but out there.

 

5.9 is at 245 hp and 335 ft·lbs
4.7 is at 235 hp and 295 ft lbs

So looking at those numbers.. Not a big enough difference to justify a new vehicle.

And not sure where you get this "max 1500 rpm" for a 4.7.

 

I used to work for a boat dealership. We used to pull a Bayliner 2355 Cierra Cruiser with a 99 Durango. It did have a 5.9 but it had no issues pulling the cruiser back and forth to boat shows. You could also look into a weight distribution hitch. http://www.etrailer.com/faq-weightdistribution.aspx
Most any trailer for a boat that size at the very least come with hydraulic brake assistance. It's not as good as electric brakes but it works pretty well. If it were me, I'd get the boat and try it. If it doesn't perform how you want, then look into getting another truck.

 

There is more to it other than the max numbers. The torque and power curves are the main thing here. True the 4.7's peak power and torque might be close to the 5.9's, but the 5.9 and 5.2 make the power much lower down in the rev band and make it for longer, which makes them more suitable for towing.

 

What I meant by that is at 1500rpm the 5.9l already is producing the same amount of torque that the 4.7l can max produce. The difference being the 4.7l has to be turning 3200rpm to reach that number. Also I think that 335ftlbs is underrated since 1996-2000 the same motor was rated ate 345ftlbs with no changes for 2001 when they dropped the rating by 10ftlbs. IIRC though the 5.9rt had 250hp and 350ftlbs. Believe me towing with a 5.9 is nicer than a 4.7 because you use way less throttle for everything. Not that the 4.7 is bad just not as good for towing as a 5.9l. Also in 1997 the 1500 ram was rated to tow 8200lbs with the 5.9 and the 3500 rams like 9000lbs with a 5.9 v8, the durango is limited by its size. So that is an expanded version (kind of) of the post that_guy has above ^

 

Just a side note, all of the SXT models I've come across have only had 2wd and 4 lock. No 4 lo.

 

One factor that I think is still in my favor is that I'll be driving at sea level on flat land to the boat ramp (about 6 miles), then the return trip.

 

honestly, the 6800 lbs is above what the driveline can handle on that rig, driveline includes brakes BTW.

If you have an owners manual it will list tow ratings based on engine size, transmission gearing, rear axle ratio, brake capability, weight and a number of other factors. They determine the weight which the vehicle can SAFELY tow. That said, there is some factor of safety built in so exceeding the weight by a little bit is not the end of the world if you are only doing it once or on rare occasions, buying your own boat and hauling it to the launch on a regular basis is NOT in my definition of rare occasions. That said i would get a bigger truck that could safely handle the size of the boat you want to get. Will the durango pull it, probably, however it will stress the components beyond what they were meant to handle and WILL cause more repairs to be necessary, and will accelerate the maintance schedule on the truck. There is also the concern of being able to control and stop the load in an emergency situation which your truck will not be able to do.

This is based on standard design practices taught to and used by engineers who design and build these things, take the information as you will

 

Sharpshooter - thanks for the reply. Agree with basic mechanical engineering principles, and why I was thinking about the beater truck. OR downgrade to a little smaller boat. Accelerated fatigue will play into this, especially with a higher than expected stresses. Engineering safety factor can be 2:1 or maybe even 3:1 (in critical applications), but as you said, based on a once in a while higher than normal stress load.

I like my D-Rex....

I think it's best if I get a beater pickup...or talk the wife into a little smaller boat!