Help Identify

That is an intake Water jacket and inspection port for an inline 4 or 6 cylinder for Mercury inboard engine. the box on the top with the 4 bolt holes usually has a screen in it to filter water flowing in to the engine. On the bottom there is a drain hole so you can flush the engine of water for winter storage. In most cases there is a petcock valve or a metal plug depending on the size it may be a 3/8" npt or a 1/2" npt . See reference below. I hope it helps.

References:

This is as close as I can come to the exact model if you look at this link you will see a similar one on this engine. All Merc and Merccruiser inboard sterndrive engines are black.

http://www.marineengine.com/parts/mercruiser-sterndrive-parts/140-gm-181-il4...

Reason:
Does not appear to be related to water or thermostat housing.

this is missing parts but it looks like a reduction gear box

References:

my mind

Reason:
Thank you. It looks more like one of the other opinions, either an exhaust elbow or water pump for a mercruiser. If possible, could you maybe find a similar one online so that I can accept it faster?