I'm helping a friend on his mercruiser 3.0
The drain plug is/was on the bottom of the exhaust manifold.
He says that water pumps through there for cooling.
If you are looking at the engine from the prop side down on it, it is on the underside on the left towards the rear.
The hole was completely stripped and partially corroded/rusted.
I tried to rethread it but the cast iron didn't take the tap very well.
My questions are:
Is there supposed to be a plug there?
Should I try to rethread to larger size?
Or should I just use a rubber expansion or test type plug like one you would use to plug a live well?
It's drill and partially threaded to 1/2x20tpi right now.