Sorry to hijack your question directed to Bill. The picture is actually from our boat.
The brand of the switch is the same as yours. However on an 54 we run a 24 volt system so most loads are producing only half the amps compared to a 12 volt system. Not so for the bowthruster, it uses about 8 kW, something like 350-400 amps @ 24v. The main switches can handle that easy as the actual switching never occurs at high amperage.
Thanks for the tip on the mechanical issues you found with the switch. Mine have been suffering from a voltage loss as well occasionally. Until now I was able to resolve this by exercising the switch a few times.