Lower unit: stud on one side, bolt on the other?

'86 Mercury 75hp. I've dropped the lower unit 5 or 6 times over the years and never paid any mind to the fact that on the underside of the cav plate, I have to remove a NUT from the stud on the port side, and a BOLT on the starboard. I just thought that's the way all motors are. I only know mine.

Now I'm prepping a used motor as a replacement, and I pulled the gearcase, and it has two studs coming straight down from the upper part. Weird. So I looked up the parts diagram HERE (#2 in that diagram), and it shows not only two studs, but that they're threaded on both ends!

So, did someone probably replace the stud on the starboard side with a bolt at some point before me, or did some variants of that motor have a stud one one side, and a bolt on the other? Whatever the reason, I have to get a new 5/8 nut now to put on the stud on the starboard side. And I guess I have to be careful when removing them, that they might loosen from the upper unit side. I didn't know they were threaded on both sides.

No big deal if they loosen up and come out. Just thread them back in like a bolt.

Yes, somebody replaced the stud with a bolt. Studs are better here because after multiple removals, a bolt can wear out the threads in an aluminum housing. Studs can be secured in place with a medium strength locking compound. Why? Because I have received repair jobs here where the nut has run down too far on the stud and the result is the stud is not going all the way to bottom........or to the collar. This will result in eventual damage to the aluminum casting threads. Then I am forced to install a helicoil, or weld solid the stripped out hole, then drill and tap to correct size.

Timguy, I like the keensert for thread repair