Prop nut size?

[wauto]

Just picked up a 1970 25hp Johnson. Problem is that it's missing the prop nut? Are the threads 5/8 x 18 ?

 

[jimmbo]

Here's the part you need
http://www.iboats.com/PROP-NUT/dm/cart_id.357252807--session_id.719860414--view_id.1495551