It didn't come with the TVs already mounted?
1&3/4" will be marginal at best for depth, the real concern is what they are screwing into. If you're not screwing into a support integrated in the wall that was designed to hold the load of a TV as you go down the road it won't be a pretty picture when you arrive at camp after a bumpy drive.
The TVs in my Hurricane use 2" screws to hold the mounts to the walls. I lowered the TV mount in the living area when I replaced the stock TV with a smart TV. They were sunk into what amounts to studs but they were not lag screws by any stretch of the imagination.