That may cost more to weld than a replacement bell housing......Especially used.

That will have to be ground to a vee on both sides and welded in stages because it's cast, not billit...
You're probably talking about a $300 weld job on a $150 part, and it would always be a weakened part.
We have run aluminum boats for decades and even I would not trust a welded together bell housing.
Just my opinion, nothing personal, but I would search for a different piece.

GT