Just my opinion, but I think the proper way to repair the crack will be as follows. NOTE: I have welded several of lower unit cracks over the years. It all comes down to how its done, and how much money the custom is wanting to spend to get it fixed. (1) Remove lower unit. (2) Remove propeller (3) Remove aluminum flang nut. (not sure if that is actually what it is called) (3)*Optional, but reccommend* Remove main propeller shaft, and seals, clean thoroughly (4) Clean all carbon deposits on the inside of the housing, and paint on the outside surrounding the cracked area. (5) Find the end of each crack. NOTE: Sometime you have put a little bit of heat on the cracked area, this will open up any hidden cracks that may not be visible. (6) Once you have located all the cracks, drill a small hole (3/16" approximately)at the end of each crack. This will prevent the crack from growing any further during the welding process. (7) Grind each crack thoroughly, making sure that the inside is ground down also. (8) Insert copper flange nut. (This will need to be fabricate by someone who has access to a lathe), this copper piece will prevent exessive damage to the internal threads. (9) Weld repair outside of the housing. Also weld what you are able to access on the inside. Be sure to allow time for the part to cool down before attempting to remove the copper flange nut. (10) After the flange nut is removed, weld the rest of the damage area. If there is any damage to the internal theads, then use a pencil grinder with the proper bit to manually cut the threads until the original flange nut can be reinstalled with out any binding. (11) Everything should now be ready for re-assembly, painting.