series connection to a single solar
controller is the least efficient set up possible, especially for panels
located on either side of the boom. So there is room for improvement.
The most efficient wiring
configuration is normally:
One controller per panel
Two controllers (one regulating the port panels and one the starboard) with the panels wired in parallel.
However, with the above configurations some care is needed with “12v” flexible panels mounted on a solid structure in hot climates to ensure that the panels maximum power point voltage does not drop below the charging
voltage required (after voltage losses in the wiring
etc). This concern is especially a consideration for 12v panels with a lower than average Vmp and unfortunately your panels fall into this category.
So I would not recommend these options in your case.
With 6 panels the best remaining option is:
Two controllers (one regulating the port panels and one the starboard) with the panels wired in series or option 2. This will produce a modest gain from option 1 and add redundancy, but it will be more expensive and involve more installation
Whether this extra cost and time is worthwhile for the modest gain is debatable and something you will have to decide for yourself. I would factor in the age of the current controller and the quality of the original wiring. The Outback controllers are very well made, but do not last forever. They can be repaired (the capacitors usually fail first), but this is usually frustrating to arrange on a cruising boat