Sorry Russ, I have to agree with Lance. When I was researching the Helen Wycherley I never found any reference to the 47ft Watson having an internal rudder, all external fittings. The 46ft and 46ft 9in Watsons had a mixture of internal and external rudders with the later builds of each batch using the external setup. As the 47ft Watsons were developments from these two classes then external wins the day.Plus all three scans that Lance has added show the external fitting.
If you blow up your b&w picture you can just make out the shaft for the rudder to the rear of the stern post, also the smudge at deck level is in the correct place for the steering box cover, difficult to see I know but unless a clearer, better angled picture comes to light I would have to fit the external rudder system.
Sorry to rain on your parade mate but that's the problem with building old lifeboats, not many of them left to nip out to look at and most of them have been messed about with during their life after the RNLI.
Mike