Pictures of the same boilers appear in "Gold for the Finding - a pictorial history of Gipplsland's Jordan Goldfield" [Tomlin, Bosa, Chamberlain - Hill of Content, 1979].
In the chapter on Blue Jacket, the authors note:
"Alluvial claims were pegged along the Jordan from the B.B. Creek to the junction with the Thomson River. Almost at the confluence of the two rivers, a sluicing operation was conducted with great thoroughness during the 1920s and 1930s. The plant was powered by a brace of boilers which had been constructed by Thompsons of Castlemaine. These still stand in situ and, unless any other arrangements are made, will be covered by the waters of the Thomson Dam."
A fuzzy photo of the the actual plant at T-J junction, dating from the 1920s is also included, plus two from the 1970s, similar to yours (but not in colour!). I suspect a trawl through Trove would elicit further; also the Mining & Geological Journal.
cheers Phil Rickard