My binnacle appears similar, but I don't see the lower portion in your
photo. Mine continues down as a closed
aluminum pipe and then to a flared base plate that is bolted to the
cockpit floor. I am able to reach the chain at the top sprocket after lifting off the compass as well as the linkage for my throtle and
gear shift. The base of my chain and it's drive mechanism operating my
hydraulic steering pump is accessable in my
engine room. The inaccessable center of the binacle tube carries the two control
cables, a 12VDC
wiring cable for compass light and mounted
electronics, and the chain. These items are fed through the tube. I can lubricate the full chain length with the access above and below when turning the
wheel.