I have a lower gear housing that got smacked on a rock and cracked. My buddy JB welded the hole and it was holding. Now it has started to leak. Can it be welded with no ill effects. By the way it is a 1987 Mercury 115. We also can not get the starter to pop. It will spin but not pop up to engage. I think there is only one solenoid and if it spins shouldn't also pop. It was popping the first time we took it out this year but my buddy messed with the wiring and now it has stopped popping. Is it the starter/solenoid/wiring? Any and all answers would be appreciated. Thanks!

The housing can be welded if the damage is minor.

The starter can be rebuilt and lubed if your mechanicly inclined.

I would replace the starter with a rebuilt unit. Probably around $125.

Nothing worse than having a unreliable starter.

Spray some WD40 on the the shaft and try it.  Sometimes the grease gets old/dry and keeps the gear from popping up.   Also make sure your battery is not weak.  If weak, it won't kick the starter fast enough to kick the bendix up.  

Depending on where the hole is in the LU.  If in an area the heat from a TIG won't damage seals, should be no problem to have it TIG'd.