I had a 2001 Jeep Cherokee, not the Grand, with an inline six and automatic. It pulled my '01 Tracker Pro185 okay, but it was sluggish in the hill country. I don't know what you should get, but that model may pull your boat okay. I got 24 MPG without the boat and about 18 MPG with it. My son has one, but his is a 2000. He said he gets 16 mph on the highway without anything in tow. Don't know what the difference might be. They appear to be rigged the same.
Now I pull with an '04 Ranger 4X4 with the 4.0 engine. It hardly knows the boat is back there and on a recent trip to Cherokee Lake in TN I averaged 19 mpg with the boat in tow. Maybe an Explorer would be a good deal. The Rangers I've had (five and counting) have all been reliable.