2005 Fiesta Vee 270 Mercruiser - Water Leak spitting from top of engine

Summerrental

I have a 2005 Rinker 270 Fiesta Vee with a Mercruiser 350 Mag MPI and Bravo Three outdrive:

So I pulled my boat for the winter yesterday and while I was on my way to the hauler I checked the engine compartment as I was idling and I saw water splattering off the top of the engine.  I kept the boat at 4-5mph for the trip to the hauler as I did not want to chance it getting worse and it was only a 10 minute ride.  When I got there I checked a bit closer and I found a hole in what looks to me as some kind of plug.  Looks similar to the brass plugs in the manifolds and risers.

This is a bit above my knowledge so I thought I’d ask here.  I am guessing it is some kind of freeze plug, but Its not one of the blue plugs that I am familiar with. As you can see in the pictures it appears that this can be unscrewed as it is threaded.  Is it as easy as unscrewing and replacing? (It’s never that easy).  Also what is the purpose of this plug and why would it rust through?

See pictures below for more clarity.  I’m sure someone here knows what this is so any suggestions would be gratefully appreciated.  Thanks in advance!

Black_Diamond

Just unscrews. Probably rusted thru the point put in for the hex during manufacturing. Use pipe dope on the threads when you replace it.  Get a bronze one and it will never happen again. 

aero3113

It should just screw out. I'm pretty sure it's just a plug that was installed instead of a temp sender.

Summerrental

Thank you, that's what I hoped.  Is it just a pipe plug like mercuruiser part 22-56800?