The dealer installed the upper and lower bolts from the inside. Threads outside on all. This is common but not ideal. The uppers have to go that way so there are no threads inside the motorwell to rub on things.
The lowers should go from outside-in with threads inside. (many service manuals actually show this) Reason is that the lower holes are always underwater. There are no flat washers to help seal up the hole because you go thru the bracket holes. The bolts are smooth most of the way with threads at the end. From outside, coat the smooth part of bolts and push thru bracket and the clean threads go in the transom hole and into the inside. No mess. Hole is fully sealed outside.
If you go the other way, the threads come into the bracket hole. There is an inch of space. Thats not easy to seal. you are blind. Also, in some cases the threads will block access to bolts holding the PTT.
I found I had a dribbly lower bolt.
Hence my newest project. I have been looking at it more today and am leaning towards not removing motors. Just clean up inside a little and,as Dennis said, get some resin in there and use two lower transom plates and be done so I can launch ontime and go fishing. I don't want project creep....
As for uppers. FYI,
if I put thick upper transom plates in motorwell, my zuke with the steering ram will be limited in up travel. It may not get all the way out of the water.