Thru hull sizes

[PabloPicasso]

I have a through hull fitting I need to replace the outside diameter is 2inches. Is this a 1-3/4"inch BSP thread size? It semis a 2" inch BSP thread is a bit over 2"inches Is that right?

 

[VicS]

I have a through hull fitting I need to replace the outside diameter is 2inches. Is this a 1-3/4"inch BSP thread size? It semis a 2" inch BSP thread is a bit over 2"inches Is that right?

2" BSP is 2.347" OD​

1¾" BSP is 2.116" OD​

1½" BSP is 1.882" OD​

1¼" BSP is 1.650" OD​

1" BSP is 1.309" OD​

 

[Daverw]

2" BSP is 2.347" OD​

1¾" BSP is 2.116" OD​

1½" BSP is 1.882" OD​

1¼" BSP is 1.650" OD​

1" BSP is 1.309" OD​

As a quick and rough guide we allow for OD to be approx the next size up, useful if going through a box of bits

 

[PabloPicasso]

Difficult to find 1-3/4 BSP through hull May be easier to get a 2 inch and bore the hole out a little bigger