Lower Unit Drain Plugs

[colbysmith]

Sorry to bring this back but, I have read that helicol does not seal well and some recommend using a mercury drain plug. However I can't find how to drill and tap to that size. Anyone know what size bit and tap to use for a mercury drain plug

Well....my main is a Merc, and my kicker is a Tohatsu. The main lower unit drain plug on my Mercury 115 4-stroke EFI is 3/8" x 16 and the Tohatsu 6hp is M8 x 1.25. Glad to see Jacks msg again while I was writing this, as at first I was worried then about using the helicoil. But he is right in that the plug seals with the gasket / washer. All I was doing was a light tug, but guess we have different versions of light tug. lol! I don't want that sucker coming loose from engine vibration, but then repairing stripped out threads is a PITA also. Colby