I have the same vehicle that you are looking at.
2005 Chevy Trailblazer 4WD
4.2L I6 3.42 Axle 5100lbs towing cap.
With a bit more boat to tow.

1991 Wellcraft 216xl Eclipse 7.4L/Bravo 1
Total weight, about 4900lb fully loaded.
The Trailblazer does an adequate job towing the load. The inline 6 is OK but I could certainly use more HP. It will frequently have to down shift on uphill sections of highway to maintain 65-70mph. Brakes are good and it tracks straight and true under hard braking.
A cross wind or a large vehicle passing can sometimes cause sway at higher speeds(>70mph). Could use a longer tounge on the trailer or a WD hitch.
Fuel economy is 17/18mpg without the trailer. Closer to 9/10 when towing. Pretty poor for a 6 cyl.
Overall, it gets the job done but a larger vehicle or TB with a V8, would be nice. With a smaller load (<4k) it does a good job and is plenty of vehicle.
