Perhaps this will help '903CAM' become the winner? It is the last clue which I can offer, then it is up to the quizmaster to decide how long to let it float before docking it.
I chose this one because it shows the river equivalent of a prime mover with dogs. Back in the days, tows could be one, two or three barges. I can't find my photo of my boat under that bridge, but I didn't need the span to be raised.
The same location, and the same event. I posted to the recent 'Haulin/Crawlin the Hume' thread that it matched the mood of major rallies over multiple hobbies. This boating one didn't have 200-400 boats, but had all the same ingredients. At the start of the day we assembled: a mixture of modern/old, large/small, commercial/private, steam/diesel. The departure was a bit spread, but the whole fleet had to meet at the bridge, because the opening time was fixed. A landmark on a journey, like reaching the top of Pretty Sally. Thereafter, boats of different abilities spread out; mates cruised together. We all pulled up for lunch, then spread again for the afternoon. At the end of the day, the mayor and town/city band were waiting to welcome us, and we partied into the night. Next day, we moved to a better spot for public viewing, along with lots of local trucks too. In great weather, the crowds came. .
I do have photos from other events at that bridge, including some with a tv helicopter hovering.
Post edited now that a winner has been announced. The bridge was built over 1925-28, intended to carry a railway extension from Victoria to NSW (that's why the highway curves onto it, the original quiz photo, taken from the Victorian side). It is in line with the 1925 extension to Yelta of the 1910 Merbein line, but there was no further extension. All Murray locks and bridges are free for boat passage, but there are restrictions on times, and a bridge lifting must be booked in advance. This one is ~9.30 and ~14.30, clear of school and commuter traffic. I am not sure of the name of the road, but it is the main route from Melbourne to Broken Hill. I crossed it first on a family holiday to Mildura, exploring historic Wentworth. I crossed it on my motorcycle and other cars, heading to railway adventures in Broken Hill. I cross over it a lot when heading to Wentworth boating and tractor events. I have passed under in several boats, including PV Coonawarra, PS Oscar W, PS Adelaide, PS Industry and my MV Jessie II.
My boat photos were taken during a 2013 major rally, marking the 150th anniversary of the first steam navigation for commerce: captains Randell and Cadell raced rival boats from Goolwa (SA) to beyond Swan Hill (Cadell had to turn back; Randell reached Maidens Punt, at today's Moama). This rally was keyed around replica paddlesteamers, and ran from Goolwa to Moama, with a few other escort boats thoughout, and varying levels of local escort boats. My photos were taken from the preserved paddlesteamer 'Oscar W': built in Echuca, operating at Goolwa today, but having done the Echuca voyage a few time in its preservation life, and often voyaging to the top of SA.