Leaking Bowman FH 410-3006 header tank

[Ghodula]

I have a small leak developing from what looks like a core plug in the side of the header tank.

Can anyone advise if this is indeed what it is and even better where I can get a replacement? I can't find a reference to it on Bowman's parts list.
If I can get it out and measure it maybe I can find a generic one to fit but I want to be sure of what it is before I start trying to remove it!

It's attached to 1972 Perking HT6354. I was considering just cleaning it down and filling it with chemical metal if it's just a plug?

 

[oldgit]

First call...Lancing Marine ?

 

[omega2]

Is there a thread in that hole, could it be an anode?

 

[bristoljim]

Looks very much like a core plug - they are just a push fit, punch out the remains being carefull not to score the casting - clean up & measure, they come in metric & imperial sizes.Any engine rebuild company / garage will carry them.
Jim