Drain plug issue 2.5l mercruiser

[Adam_c]

Hi all,
Not sure if rust got in threads but cant tighten more the a quarter turn before it pops out bought s new plug hoping it would work but didnt .should I use a tap and die set to see if I can turn it thru the block? What should/ could I do ?
thanks in advance

Adam

 

[Adam_c]

I think I've narrowed it to a 1/2 inch thread 24 pitch is this correct?

 

[alldodge]

Appears to me you have a apples and oranges thing. If that is the block drain hole then it should be 1/4NPT (National Pipe Threads). The fitting your trying to install is not pipe thread and is half of the fitting

The original fitting was installed using an extension 22-64425



Then the **** fitting 16951A1



which later was changed to 22-16951Q1



If you notice on all these fittings they all have 1/4NPT threads (red coating on the one), bur the inside was different on the drains and were machine threads and not NPT

 

[Adam_c]

Ok I think I've resolved the problem... turns out I've been trying to stick it in the wrong hole. That's a mount hole at the bottom and I assumed it was the Drain hole. The actual drain hole is higher up

 

[harringtondav]

I tried the valve fittings once, and went back to a simple brass 1/4 npt per AllDodge with a hex head. I occasionally beach my boat in river sand, and the plug allows me to poke inside the block tapped hole to release the sand and allow the block to drain. The valve fittings do not allow debris to clear. Just FYI.