Re: shift rod
You guys love to keep me guessing. If it is the straight shift rod with the small hole through the top, in the lower unit, any Merc dealer should be able to get you one. See? Now I have to guess that your 125 is older than '92.
If the break is at or near the seal, then when the welded part passes through the seal, it will leak. New part is preferable in this case
If that's the case, simply unscrew the broken rod, with the lower unit removed and lying on it's side. ( not absolutely necessary but you are less likely to shift anything) Be careful not to move the square block inside the lower unit when you unscrew then pull it out. And be prepared for some oil to come out. Slide the new one in and screw it all the way down then back out just enough to line up the hole with the linkage pin.