Looks like toast.
More concerned about the crack, or what appears to be one developing near prop shaft.
If you can weld, then the rubber seals will be goosed with the heat, plus given this is a big HP engine, then the torque of the prop-shaft and drive shaft are going to throw up all sorts of issues unless it's properly set up with shims, balanced and load tested.
Looked on Ardoran Marine's site as they're Honda dealers, but only have a 115/130hp gearbox.
This sort of thing any use? Outboard Gear Case for 2008 Honda 225 with Propeller Lower Unit | eBay
Anything local with history, then my advice would be to go for it.