I've read in other posts and on dealer web pages it's 7/8" x 14 tpi - straight thread - 1-5/16 deep. ( http://shop.torresen.com/ships_stor...m/sunfish.php?p=sunfish_deckview&ident=151447 ) I've not seen where anyone actually took a caliper and thread gauge and confirmed these numbers. Common to find a 7/8 x 14 NPT, but straight thread is tough to locate as I understand it.