1987 inline 6 90 hp Mercury water by spark plug

[randyj]

I was having trouble with this

I was having trouble with this motor running rough. I think I've got it running okay now but there is water coming out of the head around the top spark plug... I looked and there appears to be a small threaded hole next to the spark plug... am I correct that all I need to do is put a bolt/screw in there to plug the hole and everything will be okay? Can anyone tell me what that hole is for? I assume this head is like on other merc's just a cover for the water jacket.

 

[fastjeff]

It's for a pressure gage.

It's for a pressure gage. Plug it up with an 1/8 "pipe plug.

Jeff

 

[outboard_doctor]

You could have some corrosion

You could have some corrosion eating around the spark plug hole area causing the leak if the bung doesnt stop it