Yes, use one if you need to tilt it up. The latch on your motor is not designed to hold the motor bouncing down the road, which exerts much more force than WOT does.
If you don't need to tilt it up for clearance, leave it down and turn it all the way in one direction, but run a strap around it, to the trailer, not the boat. This keeps things from bouncing around. Even if you have a anti tilt latch, there is still a little play in it, and that bit of movement is heck on your motor, and transom (mostly motor).
The one real exception to using a transom saver, is for real little motors, say under 5 horse or so. If your motor mount is shaped in such a way that a block of wood wedges in snugly, and can't escape without the motor tilting up more, you can stick a block of wood in there, turn the motor all the way, and put a ratchet strap (you likely will not get enough preload out of a cambuckle strap) around the motor, down to the trailer, NOT the boat gunwales (pulling in wrong direction). For this method to work, you need a piece of hard wood (I use a scrap of teak) and a good bit of preload. If, after having strapped down, you can lift up on the lower unit, and the wood be even remotely loose, you are NOT tight enough, and it WILL come out (ask Murphy - he'll make sure of it).
Here is how I did it on my kicker. Notice my big motor is in the transom saver. If you use the over the roller mount, and you don't have power trim, you need to put a strap around it, as it will bounce off the roller, and cause real bad damage.
The only difference is, since my motor is a kicker, and I purposely have the steering adjusted as tight as it will go, so I can troll in a straight line at WOT without holding the handle, I no longer put the strap around the whole lower unit like pictured. Instead, I run it in the gap between the midsection, and the steering pivot. I do this just so I don't stress the rubber motor mounts, which would prematurely wear them out. Because the steering is set so tight, it won't flop.
