If you don't already have some way of securing your motor so it doesn't bounce when trailering you really need one. I lift my motor 2 clicks up then use a ratchet strap around the motor and secured to the corners of the trailer. It keeps the motor from bouncing which I think is harder on the motor than the transom.
I have a 115 and 9.9 hp motors on my 19' Harberraft. It not only keeps the motors from bouncing around, It saves the transom from the bouncing motors. They send the impact to the trailer and keep it off the boat. Thus the name transom saver.
I had one a long time ago for my 25 Merc. First day out the horseshoe-shaped thingy on one end popped off the trailer roller, hit the ground and snapped in two.
Don't really need it, anyway. My Merc locks down as long as it's in neutral, and it sits high enough to where it doesn't need to be tilted. I don't even tilt it when I'm launching or taking out, which freaks people out sometimes.
I think I've seen some transom savers that bolt to the trailer, rather than just sit on the roller by gravity. That seems like the way to go.
I have one of the extension transom savers that attaches to the cross bar on the rear of the trailer and extends up and cradles the lower shaft of the motor. I still have it but found that a 2/4 cut to fit across the back of the motor bracket will work just as well and is a lot easier to put on and remove and doesn't take up much room to store. I put two heavy screw eyes on the ends of the cut 2x4 and use a heavy bungy cord to strap around the motor to keep it in place. over time the motor will indent the board but not so much that you need to replace it. I have both and I use the 2x4 most of the time now.
Works great. Don't rest the motor on any of the click settings except straight up and down by itself. It will eventually bend the shaft that keeps the motor at different trim settings. Using a board or transom saver will prevent this from happening.
The skag on my 25hp Yamaha is way to close to the ground(3-4 inches) to safely trailer it. The manual says not trailer the motor in any of the up positions as the mechanism is not designed to handle the weight and may be damaged. So I have a transom saver and I have had no problems with it.