Been wondering what this plug is above my starter motor - took it off and a bunch of water came out all over the starer, so I'm guessing a water gallery??
 
Also the plug doesn't have an o-ring on it and appears to be tapered at the thread end (14mm) and is larger at the hex end (15mm); i can't seem to fit it to a thread tester as the end is chipped/corroded off...
 
Any comments are welcome.
 
Cheers,
Diskonekted

It's the block coolant drain plug, it is a tapered thread so it needs sealant on the thread, I think it is 1/4" bsp.

Yes, most likely will be BSPT (British Standard Pipe Taper).
Measure the OD about the middle of the taper. If about 13mm, then is 1/4" BSPT, or if about 16.5mm OD, then it is 3/8" BSPT. Both 19 threads/inch.
Should add that it possibly could be NPT (National pipe taper) which is 18 TPI.
 

You must be a plumber to know that!
Bunnings prolly sells those bung plugs or the local car spares shop...ya can run an aux temp gauge from there to check block heat as to the head temp .
I was told the drain plug its at the lowest point of the block so it's good to know when doing an engine out .

No not a plumber, but too many years as a mechanical & hydraulics draftsman!
Engineers supplies or hydraulic stores will definitely have them.
Cheers