Normally a TM is mounted with 4 bolts. There is no reason to use all 4 bolt holes to be able to position the motor as you want or need it. 3 bolts with washer and lock nuts is plenty enough to hold the TM properly. There is also no reason why a person could not relocate a 4th bolt position either. Some times when installing these things, the postion of the TM is the most important part. If your boat has certain things in your way, think outside the box a bit. 9 times out of 10 it's a no brainer for most.