The thru-hull on our Stb engine froze up this past visit to the boat and after trying pretty much everything to get it free we decided to replace it. The problem is that it's a very old (probably 1989 original) thru hull and ball valve that I don't see available anywhere. Most of the newer thru-hulls have the nut on the inside of the hull, but our base plate is much larger and I have my doubts as to whether the nut would grab sufficiently. The nut on the one we have has a very large flange. Here is a photo of the unit less the outside flange which we ground off.
Our base plate:
There is no manufacturer on the thing, only 1-1-2" size and 500 WOG which is Water-Oil_Gas so I'm assuming that Kha Shing didn't use a marine thru-hull. At this point we're looking at possibly using this thru-hull as a replacement: https://www.perko.com/catalog/underw..._valve_design/
The seacock choice rather than a standard thru-hull and ball valve was made as a result of reading this very fine article: