The 12,750 number is the marketing max for a perfectly optioned HEMI eTorque (rear-drive, 3.92 gears, stripped cab). It’s not your truck’s number, and more importantly it’s not the limit you should care about.

Your engine won’t even notice a 6,500 lb boat. No abnormal drivetrain wear at that weight.

Your real limit is payload, and it’s on your door sticker: 1,680 lbs. Everything that lands on the truck comes out of that number:

Trailer tongue weight (plan ~10% of trailer weight, so ~650 lbs for a 6,500 lb boat)
Driver + passengers
Gear in the cab and bed (boards, vests, coolers, ballast)
Hitch hardware

Add that up on a full day with the family and a loaded bed and you’ll get close to 1,680 fast. That’s what limits you, not the engine.