I am planning on buying a used truck and boat in the next year and am seeking feedback from owners of 2014 or 2015 sierra 1500 crew cab. The 14/15 sierra all terrains have caught my eye and recently test drove a 2015 sierra 1500 all-terrain with the 6.2L, unsure of the axle ratio.

The boat will be my first and am eyeing up a formula 292 or fountain 29 fever. Trailering would typically be 15-30 miles each way.

Is the 6.2L, 3.73, and max trailering package necessary for a 29’ boat with either single or twin engines? The 5.3L with 3.42 axle ratio can tow 9,500lbs.

Any feedback on towing with the sierra would be greatly appreciated. Thanks!

YES and that would be minimum truck for any boat in that size range.
Dry weight will be 6-7k plus steel trailer, fuel and gear and you'll be at 9-10k loaded

Get the 6.2 with max tow. This truck has a 7600 GVW instead of 7200, bigger rear end, more cooling and much more HP and torque. I have a 2016 and it handles my 29 Fountain fine.

Agreed with above! If not a 6.2, make sure you get at least. A 5.3 with a 3.42 or higher if available, i cant recal. Dont get a 3.08 with a 5.3, it is day and night towing with a 3.42 vs 3.08
You will be in the right truck!

The 14/15 GM half tons are far better trucks than they have ever built. My 2015 Silverado double cab 5.3 with 3.42 gears does every single thing better (accelerating load, stability, handling) than my 03 Avalanche 2500 with the 8.1L and 4.10 gears did. You will be fine pulling what you have listed with either the 5.3 or the 6.2. Don't count the 5.3 out if you can get one cheap. I pull my 380 Powerquest around town with my silverado and it handles that load far far better than it should. Proper trailer balance and setup helps a ton though. Would I go cross country with it or in the mountains? heck no, but in the flat area I live in, no issues. The new half tons are more truck than the early 2000's 3/4 tons were.

I have a 5.3/3.42 Silverado and I love it, but I'm only towing a 24' (actually 25' with platform, and 550lbs of motor waaaay at the back, up high.) Still, I wish I had bought a Max Tow/NHT for the better rear axle, spring and brake controller. I wouldn't pull a twin BBC 29' with my truck on a long haul; don't even think I'd do it for regular 60 mile trips. The 6.2/NHT is more suited for it, a large portion of depreciation on a '14 is mostly done by now, and pretty much everything on the K2XX is better than the GMT900.

As for weight distribution/trailer set up.... it only took one "pucker" moment in the Poconos for me to ascertain that as good as the truck is, it isn't as long or heavy as a 2500 CCLB diesel. There is no replacement for sheer vehicle weight and wheelbase when towing.

I have 15 crew 4wd 8 speed 6.2 with 3.23 and pull about 7800 loaded. The truck is hands down better than the 08 I had with a 5.3. Additionally the truck is fun to drive for being 5500 lbs it is no sports car but a good daily driver. The bad,the 8 speed transmission is crap good for gas mileage but the tune and refinement sucks. Mine has already been pulled at 12k miles and torque converter replaced, still clunks a lot. Look on the GM truck forums for the issues. End of the day love the truck wish I bought a 14 with 6 speed and 6.2.

I also added air bags the new trucks have softer springs and it really helps on long hauls

I pull my '79 Formula 255 Liberator (7500# w/trailer and fuel) with a '16 Yukon 5.3 w/Max Tow (3:42's and Auto Level Rear Suspension). It does a great job here in South Florida and even with 2 wheel drive pulls my Old Formula out of the water at low tide with no problems. I'm running 600# Tongue Weight and it pulls perfectly at 70 with no sway.

The 5.3/6 Speed/3:42 set up is a great towing combination. The 6 speed with 3:42's has the same 1st gear over all that the old 4 speeds did with 4.10's...big difference !!

The Max Tow rating in a Standard Wheelbase Yukon or Tahoe is 8500#.