Drain bushing in mercruiser engine block

[witchy woman]

1999 (enginge year) mercruiser 305. I need to replace one of the brass drain bushings that go in the sides of the engine block and hold the little blue butterfly drain screws. The bushing is Merc part 22860088. I need to chase the threads in the block in order to install a new bushing. Can anyone tell me the MALE thread pattern?

 

[alldodge]

1999 (enginge year) mercruiser 305. I need to replace one of the brass drain bushings that go in the sides of the engine block and hold the little blue butterfly drain screws. The bushing is Merc part 22860088. I need to chase the threads in the block in order to install a new bushing. Can anyone tell me the MALE thread pattern?

The one in the cast iron block is 1/4 NPT (National Pipe Thread)

 

[UncleWillie]

And before you complain that it is a lot bigger than 1/4 inch....
NPT is identified by the approximate diameter of the Inside of the pipe Not the Outside threads.
1/4 NPT is larger than 1/2 inch actual diameter. Almost big enough to stick your little finger in the hole.

 

[Scott Danforth]

if you just need to chase the threads. you will only need about a 1/2 turn of the pipe tap. the pipe threads are tapered. However if the threads are really buggered up, you can get away with threading deeper, however you will have to trim the fitting a bit.

remember, this is cast iron, so grease the tap.